AT83C51RB2/RC2

Features
• 80C52 Compatible
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
– Four 8-bit I/O Ports
– Three 16-bit Timer/Counters
– 256 Bytes Scratch Pad RAM
– 8 Interrupt Sources with 4 Priority Levels
– Dual Data Pointer
Variable Length MOVX for Slow RAM/Peripherals
High-speed Architecture
– 10 to 40 MHz in Standard Mode
16K/32K Bytes On-Chip ROM Program
On-Chip 1024 bytes Expanded RAM (XRAM)
– Software Selectable Size (0, 256, 512, 768, 1024 bytes)
– 256 Bytes Selected at Reset
Keyboard Interrupt Interface on Port P1
8-bit Clock Prescaler
64K Program and Data Memory Spaces
Improved X2 Mode with Independant Selection for CPU and Each Peripheral
Programmable Counter Array 5 Channels with:
– High-speed Output
– Compare/Capture
– Pulse Width Modulator
– Watchdog Timer Capabilities
Asynchronous Port Reset
Full Duplex Enhanced UART
Dedicated Baud Rate Generator for UART
Low EMI (Inhibit ALE)
Hardware Watchdog Timer (One-time Enabled with Reset-out)
Power Control Modes
– Idle Mode
– Power-down Mode
– Power-off Flag
Power Supply: 2.7V to 5.5V
Temperature Ranges: Commercial (0 to +70°C) and Industrial (-40°C to +85°C)
Packages: PDIL40, PLCC44, VQFP44
80C51 High
Performance
ROM 8-bit
Microcontroller
AT83C51RB2
AT83C51RC2
1. Description
AT8xC51Rx2 microcontrollers are high performance ROM versions of the 80C51 8-bit microcontrollers. They contain a 0K, 16K or 32K bytes ROM memory block for program.
The microcontrollers retain all features of the Atmel 80C52 with 256 bytes of internal RAM, a 7source 4-level interrupt controller and three timer/counters.
In addition, the microcontrollers have a Programmable Counter Array, an XRAM of 1024 byte, a
Hardware Watchdog Timer, a Keyboard Interface, a more versatile serial channel that facilitates
multiprocessor communication (EUART) and a speed improvement mechanism (X2 mode).
The microcontrollers have 2 software-selectable modes of reduced activity and 8 bit clock prescaler for further reduction in power consumption. In Idle mode, the CPU is frozen while the
peripherals and the interrupt system are still operating. In the Power-down mode, the RAM is
saved and all other functions are inoperative.
Table 1. Memory Size
ROM (Bytes)
XRAM (Bytes)
TOTAL RAM (Bytes)
I/O
AT83C51RB2
16K
1024
1280
32
AT83C51RC2
32K
1024
1280
32
(2) (2)
XTAL1
XTAL2
RAM
256x8
C51
CORE
PSEN
ROM
32Kx8 or
16Kx8
XRAM
PCA
1Kx8
T2
T2EX
(1) (1)
(1)
EUART
+
BRG
ALE/ PROG
PCA
ECI
Vss
VCC
TxD
RxD
2. Block Diagram
(1)
Timer2
IB-bus
CPU
EA
Timer 0
Timer 1
(2)
Notes:
2
INT
Ctrl
Parallel I/O Ports & Ext. Bus
Watch
Dog
Key
Board
P3
P2
P1
P0
INT1
(2) (2)
T1
(2) (2)
INT0
Port 0 Port 1 Port 2 Port 3
RESET
WR
(2)
T0
RD
1. Alternate function of Port 1
2. Alternate function of Port 3
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
3. Pin Configurations
P1.0/T2
1
40
VCC
P1.1/T2EX
2
P0.0/AD0
P1.2/ECI
P1.3CEX0
P1.4/CEX1
3
4
39
38
P1.5/CEX2
P1.6/CEX3
37
P0.1/AD1
P0.2/AD2
6
36
35
P0.3/AD3
P0.4/AD4
7
8
34
33
P0.5/AD5
9
32
P0.7/AD7
10
31
30
EA
ALE/PROG
13
29
28
P3.5/T1
14
15
27
26
PSEN
P2.7/AD15
P2.6/AD14
P2.5/AD13
P3.6/WR
16
25
P3.7/RD
XTAL2
17
18
24
23
P2.2/AD10
XTAL1
19
20
22
21
P2.1/AD9
VSS
P0.2/AD2
P0.3/AD3
P0.1/AD1
P0.0/AD0
VCC
NIC*
P1.0/T2
P1.1/T2EX
P3.4/T0
P1.2/ECI
P3.2/INT0
P3.3/INT1
PDIL40
11
12
P1.3/CEX0
P3.0/RxD
P3.1/TxD
P0.6/AD6
P1.4/CEX1
P1.7CEX4
RST
5
6 5 4 3 2 1 44 43 42 41 40
P2.4/AD12
P2.3/AD11
P1.5/CEX2
P2.0/AD8
P1.6/CEX3
7
8
39
38
P0.4/AD4
P1.7/CEx4
9
37
RST
P0.6/AD6
10
36
P3.0/RxD
P0.7/AD7
NIC*
11
12
35
34
EA
P3.1/TxD
13
33
P3.2/INT0
ALE/PROG
14
15
32
31
PSEN
16
30
P2.6/A14
17
29
P2.5/A13
P3.3/INT1
P3.4/T0
P3.5/T1
PLCC44
P0.5/AD5
NIC*
P2.7/A15
P2.3/A11
P2.4/A12
P2.2/A10
P2.1/A9
NIC*
P2.0/A8
VSS
XTAL1
XTAL2
P3.7/RD
P3.6/WR
P0.3/AD3
P0.2/AD2
P0.1/AD1
P0.0/AD0
VCC
NIC*
P1.0/T2
P1.1/T2EX
P1.2/ECI
P1.3/CEX0
P1.4/CEX1
18 19 20 21 22 23 24 25 26 27 28
44 43 42 41 40 39 38 37 36 35 34
33
32
P0.4/AD4
31
P0.6/AD6
30
P0.7/AD7
29
28
EA
27
ALE/PROG
PSEN
9
26
25
10
24
P2.6/A14
11
23
P2.5/A13
P1.5/CEX2
1
P1.6/CEX3
P1.7/CEX4
2
RST
3
4
P3.0/RxD
5
NIC*
P3.1/TxD
P3.2/INT0
P3.3/INT1
P3.4/T0
P3.5/T1
VQFP44 1.4
6
7
8
P0.5/AD5
NIC*
P2.7/A15
P2.3/A11
P2.4/A12
P2.2/A10
P2.1/A9
NIC*
P2.0/A8
VSS
XTAL1
XTAL2
P3.7/RD
P3.6/WR
12 13 14 15 16 17 18 19 20 21 22
*NIC: No Internal Connection
3
4114B–8051–01/09
Table 3-1.
Pin Description
Pin Number
Mnemonic
DIL
PLCC44
VQFP44 1.4
Type
Name and Function
VSS
20
22
16
I
Ground: 0V reference
VCC
40
44
38
I
Power Supply: This is the power supply voltage for normal, idle and power-down
operation
P0.0 - P0.7
39 - 32
43 - 36
37 - 30
I/O
Port 0: Port 0 is an open-drain, bi-directional I/O port. Port 0 pins that have 1s
written to them float and can be used as high impedance inputs. Port 0 must be
polarized to VCC or VSS in order to prevent any parasitic current consumption. Port
0 is also the multiplexed low-order address and data bus during access to external
program and data memory. In this application, it uses strong internal pull-up when
emitting 1s. Port 0 also inputs the code bytes during EPROM programming.
External pull-ups are required during program verification during which P0 outputs
the code bytes.
P1.0 - P1.7
1-8
2-9
40 - 44
1-3
I/O
Port 1: Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. Port 1 pins
that have 1s written to them are pulled high by the internal pull-ups and can be
used as inputs. As inputs, Port 1 pins that are externally pulled low will source
current because of the internal pull-ups. Port 1 also receives the low-order address
byte during memory programming and verification.
Alternate functions for T89C51RB2/RC2 Port 1 include:
1
2
2
3
40
41
I/O
P1.0: Input/Output
I/O
T2 (P1.0): Timer/Counter 2 external count input/Clockout
I/O
P1.1: Input/Output
I
3
4
42
I/O
I
4
5
6
7
8
5
6
7
8
9
43
44
1
2
3
T2EX: Timer/Counter 2 Reload/Capture/Direction Control
P1.2: Input/Output
ECI: External Clock for the PCA
I/O
P1.3: Input/Output
I/O
CEX0: Capture/Compare External I/O for PCA module 0
I/O
P1.4: Input/Output
I/O
CEX1: Capture/Compare External I/O for PCA module 1
I/O
P1.5: Input/Output
I/O
CEX2: Capture/Compare External I/O for PCA module 2
I/O
P1.6: Input/Output
I/O
CEX3: Capture/Compare External I/O for PCA module 3
I/O
P1.7: Input/Output:
I/O
CEX4: Capture/Compare External I/O for PCA module 4
XTAL1
19
21
15
I
Crystal 1: Input to the inverting oscillator amplifier and input to the internal clock
generator circuits.
XTAL2
18
20
14
O
Crystal 2: Output from the inverting oscillator amplifier
4
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 3-1.
Pin Description (Continued)
Pin Number
Mnemonic
DIL
PLCC44
VQFP44 1.4
Type
P2.0 - P2.7
21 - 28
24 - 31
18 - 25
I/O
Name and Function
Port 2: Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. Port 2 pins
that have 1s written to them are pulled high by the internal pull-ups and can be
used as inputs. As inputs, Port 2 pins that are externally pulled low will source
current because of the internal pull-ups. Port 2 emits the high-order address byte
during fetches from external program memory and during accesses to external
data memory that use 16-bit addresses (MOVX @DPTR). In this application, it
uses strong internal pull-ups emitting 1s. During accesses to external data memory
that use 8-bit addresses (MOVX @Ri), Port 2 emits the contents of the P2 SFR.
Some Port 2 pins receive the high order address bits during ROM reading and
verification:
P2.0 to P2.5 for 16 KB devices
P2.0 to P2.6 for 32 KB devices
P3.0 - P3.7
10 - 17
11,
13 - 19
5,
7 - 13
I/O
Port 3: Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. Port 3 pins
that have 1s written to them are pulled high by the internal pull-ups and can be
used as inputs. As inputs, Port 3 pins that are externally pulled low will source
current because of the internal pull-ups. Port 3 also serves the special features of
the 80C51 family, as listed below.
10
11
5
I
RXD (P3.0): Serial input port
11
13
7
O
TXD (P3.1): Serial output port
12
14
8
I
INT0 (P3.2): External interrupt 0
13
15
9
I
INT1 (P3.3): External interrupt 1
14
16
10
I
T0 (P3.4): Timer 0 external input
15
17
11
I
T1 (P3.5): Timer 1 external input
16
18
12
O
WR (P3.6): External data memory write strobe
17
19
13
O
RD (P3.7): External data memory read strobe
Reset: A high on this pin for two machine cycles while the oscillator is running,
resets the device. An internal diffused resistor to VSS permits a power-on reset
using only an external capacitor to VCC. This pin is an output when the hardware
watchdog forces a system reset.
RST
9
10
4
I/O
ALE/PROG
30
33
27
O (I)
Address Latch Enable/Program Pulse: Output pulse for latching the low byte of
the address during an access to external memory. In normal operation, ALE is
emitted at a constant rate of 1/6 (1/3 in X2 mode) the oscillator frequency, and can
be used for external timing or clocking. Note that one ALE pulse is skipped during
each access to external data memory. This pin is also the program pulse input
(PROG) during Flash programming. ALE can be disabled by setting SFR’s AUXR.0
bit. With this bit set, ALE will be inactive during internal fetches.
PSEN
29
32
26
O
Program Strobe Enable: The read strobe to external program memory. When
executing code from the external program memory, PSEN is activated twice each
machine cycle, except that two PSEN activations are skipped during each access
to external data memory. PSEN is not activated during fetches from internal
program memory.
EA
31
35
29
I
External Access Enable: EA must be externally held low to enable the device to
fetch code from external program memory locations. If security level 1 is
programmed, EA will be internally latched on Reset.
5
4114B–8051–01/09
4. SFR Mapping
The Special Function Registers (SFRs) of the microcontroller fall into the following categories:
• C51 core registers: ACC, B, DPH, DPL, PSW, SP
• I/O port registers: P0, P1, P2, P3
• Timer registers: T2CON, T2MOD, TCON, TH0, TH1, TH2, TMOD, TL0, TL1, TL2, RCAP2L,
RCAP2H
• Serial I/O port registers: SADDR, SADEN, SBUF, SCON
• PCA (Programmable Counter Array) registers: CCON, CCAPMx, CL, CH, CCAPxH,
CCAPxL (x: 0 to 4)
• Power and clock control registers: PCON
• Hardware Watchdog Timer registers: WDTRST, WDTPRG
• Interrupt system registers: IE0, IPL0, IPH0, IE1, IPL1, IPH1
• Keyboard Interface registers: KBE, KBF, KBLS
• BRG (Baud Rate Generator) registers: BRL, BDRCON
• Clock Prescaler register: CKRL
• Others: AUXR, AUXR1, CKCON0, CKCON1
6
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 3 shows all SFRs with their address and their reset value.
Table 4-1.
SFR Mapping
Bit
Addressable
0/8
F8h
F0h
D8h
1/9
2/A
3/B
4/C
5/D
6/E
CH
CCAP0H
CCAP1H
CCAPL2H
CCAPL3H
CCAPL4H
0000 0000
XXXX XXXX
XXXX XXXX
XXXX XXXX
XXXX XXXX
XXXX XXXX
7/F
FFh
F7h
B
0000 0000
E8h
E0h
Non-bit Addressable
CL
CCAP0L
CCAP1L
CCAPL2L
CCAPL3L
CCAPL4L
0000 0000
XXXX XXXX
XXXX XXXX
XXXX XXXX
XXXX XXXX
XXXX XXXX
EFh
E7h
ACC
0000 0000
CCON
CMOD
CCAPM0
CCAPM1
CCAPM2
CCAPM3
CCAPM4
00X0 0000
00XX X000
X000 0000
X000 0000
X000 0000
X000 0000
X000 0000
D0h
PSW
0000 0000
C8h
T2CON
0000 0000
DFh
D7h
T2MOD
XXXX XX00
RCAP2L
0000 0000
RCAP2H
0000 0000
TL2
0000 0000
CFh
TH2
0000 0000
C0h
B8h
B0h
A8h
A0h
98h
90h
88h
80h
C7h
IPL0
SADEN
X000 000
0000 0000
BFh
P3
IE1
IPL1
IPH1
IPH0
1111 1111
XXXX XXX0b
XXXX XXX0b
XXXX XXX0b
X000 0000
IE0
SADDR
0000 0000
0000 0000
B7h
AFh
P2
AUXR1
WDTRST
WDTPRG
1111 1111
XXXX XXX0
XXXX XXXX
XXXX X000
SCON
SBUF
BRL
BDRCON
KBLS
KBE
KBF
0000 0000
XXXX XXXX
0000 0000
XXX0 0000
0000 0000
0000 0000
0000 0000
9Fh
P1
CKRL
1111 1111
1111 1111
TCON
TMOD
TL0
TL1
TH0
TH1
0000 0000
0000 0000
0000 0000
0000 0000
0000 0000
0000 0000
P0
1111 1111
SP
0000 0111
DPL
0000 0000
DPH
0000 0000
0/8
1/9
2/A
3/B
AUXR
XX0X 0000
A7h
CKCON0
97h
8Fh
0000 0000
PCON
87h
00X1 0000
4/C
5/D
6/E
7/F
Reserved
7
4114B–8051–01/09
5. Oscillators
5.1
Overview
One oscillator is available for CPU:
• OSC used for high frequency (3 MHz to 40 MHz)
In order to optimize the power consumption and the execution time needed for a specific task,
an internal prescaler feature has been implemented between the selected oscillator and the
CPU.
5.2
Registers
Table 5-1.
Clock Reload Register
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit
Number
Bit
Mnemonic
7:0
CKRL
Description
Clock Reload Register: Prescaler value
Reset Value = 1111 1111b
Not bit addressable
5.2.1
Prescaler Divider
A hardware RESET puts the prescaler divider in the following state:
• CKRL = FFh: FCLK CPU = FCLK PERIPH = FOSC/2 (Standard C51 feature)
KS signal selects OSC: FCLK OUT = FOSC
• Any value between FFh down to 00h can be written by software into CKRL register in order to
divide frequency of the selected oscillator:
– CKRL = 00h: minimum frequency
FCLK CPU = FCLK PERIPH = FOSC/1020 (Standard Mode)
FCLK CPU = FCLK PERIPH = FOSC/510 (X2 Mode)
– CKRL = FFh: maximum frequency
FCLK CPU = FCLK PERIPH = FOSC/2 (Standard Mode)
FCLK CPU = FCLK PERIPH = FOSC (X2 Mode)
– FCLK CPU and FCLK PERIPH
In X2 mode:
F OSC
F CPU = F CLKPERIPH = ---------------------------------------------
2 × ( 255 – CKRL )
In X1 mode:
8
F OSCA
F CPU = F CLKPERIPH = --------------------------------------------4 × ( 255 – CKRL )
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
6. Enhanced Features
In comparison to the original 80C52, the microcontrollers implement the following new features:
• X2 option
• Dual Data Pointer
• Extended RAM
• Programmable Counter Array (PCA)
• Hardware Watchdog
• 4-level Interrupt Priority System
• Power-off Flag
• Power On Reset
• ONCE mode
• ALE disabling
• Some enhanced features are also located in the UART and the Timer 2
6.1
X2 Feature and OSC Clock Generation
The microcontroller core needs only 6 clock periods per machine cycle. This feature called ”X2”
provides the following advantages:
• Divides frequency crystals by 2 (cheaper crystals) while keeping same CPU power.
• Saves power consumption while keeping same CPU power (oscillator power saving).
• Saves power consumption by dividing dynamically the operating frequency by 2 in operating
and idle modes.
• Increases CPU power by 2 while keeping same crystal frequency.
In order to keep the original C51 compatibility, a divider by 2 is inserted between the XTAL1 signal and the main clock input of the core (phase generator). This divider may be disabled by
software.
6.1.1
Description
The clock for the whole circuit and peripherals is first divided by two before being used by the
CPU core and the peripherals.
This allows any cyclic ratio to be accepted on XTAL1 input. In X2 mode, as this divider is
bypassed, the signals on XTAL1 must have a cyclic ratio between 40 to 60%.
Figure 6-1 shows the clock generation block diagram. X2 bit is validated on the rising edge of
the XTAL1 ÷ 2 to avoid glitches when switching from X2 to standard mode. Figure 6-2 shows the
switching mode waveforms.
Figure 6-1.
Clock Generation Diagram
CKRL
2
XTAL1
FXTAL
FOSC
XTAL1:2
0
1
CLK Periph
8-bit Prescaler
Idle
CLK CPU
X2
CKCON0
9
4114B–8051–01/09
Figure 6-2.
Mode Switching Waveforms
XTAL1
XTAL1:2
X2 Bit
FOSC
CPU Block
STD Mode
X2 Mode
STD Mode
The X2 bit in the CKCON0 register (see Table 6-1) allows to switch from 12 clock periods per
instruction to 6 clock periods and vice versa. At reset, the speed is set according to X2 bit of
Hardware Config Byte (HCB). By default, Standard mode is activated. Setting the X2 bit activates the X2 feature (X2 mode).
The T0X2, T1X2, T2X2, UARTX2, PCAX2 and WDX2 bits in the CKCON0 register (Table 6-1)
allow to switch from standard peripheral speed (12 clock periods per peripheral clock cycle) to
fast peripheral speed (6 clock periods per peripheral clock cycle). These bits are active only in
X2 mode.
Table 6-1.
CKCON0 Register
CKCON0 - Clock Control Register (8Fh)
7
6
5
4
3
2
1
0
-
WDX2
PCAX2
SIX2
T2X2
T1X2
T0X2
X2
Bit
Bit
Number
Mnemonic
7
-
6
WDX2
Description
Reserved
Do not set this bit.
Watchdog clock (This control bit is validated when the CPU clock X2 is set; when X2
is low, this bit has no effect).
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
10
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Bit
Bit
Number
Mnemonic
5
PCAX2
Description
Programmable Counter Array clock (This control bit is validated when the CPU
clock X2 is set; when X2 is low, this bit has no effect).
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
4
SIX2
Enhanced UART clock (Mode 0 and 2) (This control bit is validated when the CPU
clock X2 is set; when X2 is low, this bit has no effect).
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
3
T2X2
Timer 2 clock (This control bit is validated when the CPU clock X2 is set; when X2 is
low, this bit has no effect).
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle.
2
T1X2
Timer 1 clock (This control bit is validated when the CPU clock X2 is set; when X2 is
low, this bit has no effect).
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle
1
T0X2
Timer 0 clock (This control bit is validated when the CPU clock X2 is set; when X2 is
low, this bit has no effect).
Cleared to select 6 clock periods per peripheral clock cycle.
Set to select 12 clock periods per peripheral clock cycle
CPU clock
0
X2
Cleared to select 12 clock periods per machine cycle (STD mode) for CPU and all the
peripherals.
Set to select 6clock periods per machine cycle (X2 mode) and to enable the individual
peripherals "X2" bits.
Programmed by hardware after Power-up regarding Hardware Config Byte (HCB).
Reset Value = 0000 000’HCB.X2’b (see Hardware Config Byte)
Not bit addressable
11
4114B–8051–01/09
7. Dual Data Pointer Register
The additional data pointer can be used to speed up code execution and reduce code size.
The dual DPTR structure is a way by which the chip will specify the address of an external data
memory location. There are two 16-bit DPTR registers that address the external memory, and a
single bit called DPS = AUXR1.0 (see Table 7-1) that allows the program code to switch
between them (Refer to Figure 7-1).
Figure 7-1.
Use of Dual Pointer
External Data Memory
7
0
DPS
DPTR1
DPTR0
AUXR1(A2H)
DPH(83H) DPL(82H)
Table 7-1.
AUXR1 Register
AUXR1- Auxiliary Register 1(0A2h)
7
6
5
4
3
2
1
0
-
-
-
-
GF3
0
-
DPS
Bit
Number
Bit
Mnemonic
7
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
5
-
Reserved
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
GF3
2
0
Always cleared(1).
1
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
0
DPS
Description
This bit is a general purpose user flag.
Data Pointer Selection
Cleared to select DPTR0.
Set to select DPTR1.
Reset Value: XXXX XXXX0b
Not bit addressable
Note:
12
1. Bit 2 stuck at 0; this allows to use INC AUXR1 to toggle DPS without changing GF3.
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
7.1
Assembly Language
; Block move using dual data pointers
; Modifies DPTR0, DPTR1, A and PSW
; note: DPS exits opposite of entry state
; unless an extra INC AUXR1 is added
;
00A2 AUXR1 EQU 0A2H
;
0000 909000MOV DPTR,#SOURCE ; address of SOURCE
0003 05A2 INC AUXR1 ; switch data pointers
0005 90A000 MOV DPTR,#DEST ; address of DEST
0008 LOOP:
0008 05A2 INC AUXR1 ; switch data pointers
000A E0 MOVX A,@DPTR ; get a byte from SOURCE
000B A3 INC DPTR ; increment SOURCE address
000C 05A2 INC AUXR1 ; switch data pointers
000E F0 MOVX @DPTR,A ; write the byte to DEST
000F A3 INC DPTR ; increment DEST address
0010 70F6JNZ LOOP ; check for 0 terminator
0012 05A2 INC AUXR1 ; (optional) restore DPS
INC is a short (2 bytes) and fast (12 clocks) way to manipulate the DPS bit in the AUXR1 SFR.
However, note that the INC instruction does not directly force the DPS bit to a particular state,
but simply toggles it. In simple routines, such as the block move example, only the fact that DPS
is toggled in the proper sequence matters, not its actual value. In other words, the block move
routine works the same whether DPS is '0' or '1' on entry. Observe that without the last instruction (INC AUXR1), the routine will exit with DPS in the opposite state.
13
4114B–8051–01/09
8. Expanded RAM (XRAM)
The AT83C51RB2/RC2 devices provide additional Bytes of Random Access Memory (RAM)
space for increased data parameter handling and high level language usage.
The devices have expanded RAM in external data space; maximum size and location are
described in Table 8-1.
Table 8-1.
Expanded RAM
Address
AT83C51RB2/RC2
XRAM size
Start
End
1024
00h
3FFh
The AT83C51RB2/RC2 has internal data memory that is mapped into four separate segments.
The four segments are:
1. The Lower 128 bytes of RAM (addresses 00h to 7Fh) are directly and indirectly
addressable.
2. The Upper 128 bytes of RAM (addresses 80h to FFh) are indirectly addressable only.
3. The Special Function Registers (SFRs) (addresses 80h to FFh) are directly addressable only.
4. The expanded RAM bytes are indirectly accessed by MOVX instructions, and with the
EXTRAM bit cleared in the AUXR register (see Table 8-1).
The lower 128 bytes can be accessed by either direct or indirect addressing. The Upper 128
bytes can be accessed by indirect addressing only. The Upper 128 bytes occupy the same
address space as the SFR. That means they have the same address, but are physically separate from SFR space.
Figure 8-1.
Internal and External Data Memory Address
0FFh or 3FFh
0FFh
0FFh
Upper
128 Bytes
Internal
RAM
indirect accesses
XRAM
80h
0FFFFh
Special
Function
Register
Direct Accesses
External
Data
Memory
80h
7Fh
Lower
128 Bytes
Internal
RAM
Direct or Indirect
Accesses
00
00
00FFh up to 03FFh
0000
When an instruction accesses an internal location above address 7Fh, the CPU knows whether
the access is to the upper 128 bytes of data RAM or to SFR space by the addressing mode used
in the instruction.
• Instructions that use direct addressing access SFR space. For example: MOV 0A0H, # data,
accesses the SFR at location 0A0h (which is P2).
14
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
• Instructions that use indirect addressing access the Upper 128 bytes of data RAM. For
example: MOV @R0, # data where R0 contains 0A0h, accesses the data byte at address
0A0h, rather than P2 (whose address is 0A0h).
• The XRAM bytes can be accessed by indirect addressing, with EXTRAM bit cleared and
MOVX instructions. This part of memory which is physically located on-chip, logically
occupies the first bytes of external data memory. The bits XRS0 and XRS1 are used to hide a
part of the available XRAM as explained in Table 8-1. This can be useful if external
peripherals are mapped at addresses already used by the internal XRAM.
• With EXTRAM = 0, the XRAM is indirectly addressed, using the MOVX instruction in
combination with any of the registers R0, R1 of the selected bank or DPTR. An access to
XRAM will not affect ports P0, P2, P3.6 (WR) and P3.7 (RD). For example, with EXTRAM =
0, MOVX @R0, # data where R0 contains 0A0H, accesses the XRAM at address 0A0H
rather than external memory. An access to external data memory locations higher than the
accessible size of the XRAM will be performed with the MOVX DPTR instructions in the same
way as in the standard 80C51, with P0 and P2 as data/address busses, and P3.6 and P3.7
as write and read timing signals. Accesses to XRAM above 0FFH can only be done by the
use of DPTR.
• With EXTRAM = 1, MOVX @Ri and MOVX @DPTR will be similar to the standard 80C51.
MOVX @ Ri will provide an eight-bit address multiplexed with data on Port 0 and any output
port pins can be used to output higher order address bits. This is to provide the external
paging capability. MOVX @DPTR will generate a sixteen-bit address. Port2 outputs the highorder eight address bits (the contents of DPH) while Port0 multiplexes the low-order eight
address bits (DPL) with data. MOVX @ Ri and MOVX @DPTR will generate either read or
write signals on P3.6 (WR) and P3.7 (RD).
The stack pointer (SP) may be located anywhere in the 256 bytes RAM (lower and upper RAM)
internal data memory. The stack may not be located in the XRAM.
The M0 bit allows to stretch the XRAM timings; if M0 is set, the read and write pulses are
extended from 6 to 30 clock periods. This is useful to access external slow peripherals.
Table 8-2.
AUXR Register
AUXR - Auxiliary Register (8Eh)
7
6
5
4
3
2
1
0
-
-
M0
-
XRS1
XRS0
EXTRAM
AO
Bit
Bit
Number
Mnemonic
7
-
6
-
Description
Reserved
The value read from this bit is indeterminate. Do not set this bit
Reserved
The value read from this bit is indeterminate. Do not set this bit
Pulse length
5
M0
Cleared to stretch MOVX control: the RD and the WR pulse length is 6 clock periods
(default).
Set to stretch MOVX control: the RD and the WR pulse length is 30 clock periods.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit
15
4114B–8051–01/09
Bit
Bit
Number
Mnemonic
Description
3
XRS1
XRAM Size
2
XRS0
XRS1
0
XRS0
0
XRAM Size
256 bytes (default)
0
1
512 bytes
1
0
768 bytes
1
1
1024 bytes
EXTRAM bit
Cleared to access internal XRAM using MOVX @ Ri/ @ DPTR.
1
EXTRAM
Set to access external memory.
Programmed by hardware after Power-up regarding Hardware Security Byte (HSB),
default setting, XRAM selected.
0
AO
ALE Output bit
Cleared, ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if X2
mode is used) (default). Set, ALE is active only if a MOVX or MOVC instruction is used.
Reset Value = XX0X 00’HSB.XRAM’0b (see Table 8-1)
Not bit addressable
16
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
9. Timer 2
The Timer 2 in the AT83C51RB2/RC2 is the standard C52 Timer 2.
It is a 16-bit timer/counter: the count is maintained by two eight-bit timer registers, TH2 and TL2
are cascaded. It is controlled by T2CON (Table 9-1) and T2MOD (Table 9-2) registers. Timer 2
operation is similar to Timer 0 and Timer 1. C/T2 selects FOSC/12 (timer operation) or external
pin T2 (counter operation) as the timer clock input. Setting TR2 allows TL2 to be incremented by
the selected input.
Timer 2 has 3 operating modes: capture, auto-reload and Baud Rate Generator. These modes
are selected by the combination of RCLK, TCLK and CP/RL2 (T2CON).
Refer to the Atmel 8-bit Microcontroller Hardware description for Capture and Baud Rate Generator Modes.
Timer 2 includes the following enhancements:
• Auto-reload mode with up or down counter
• Programmable clock-output
9.1
Auto-reload Mode
The auto-reload mode configures Timer 2 as a 16-bit timer or event counter with automatic
reload. If DCEN bit in T2MOD is cleared, Timer 2 behaves as in 80C52 (refer to the Atmel 8-bit
Microcontroller Hardware description). If DCEN bit is set, Timer 2 acts as an Up/down
timer/counter as shown in Figure 9-1. In this mode the T2EX pin controls the direction of count.
When T2EX is high, Timer 2 counts up. Timer overflow occurs at FFFFh which sets the TF2 flag
and generates an interrupt request. The overflow also causes the 16-bit value in RCAP2H and
RCAP2L registers to be loaded into the timer registers TH2 and TL2.
When T2EX is low, Timer 2 counts down. Timer underflow occurs when the count in the timer
registers TH2 and TL2 equals the value stored in RCAP2H and RCAP2L registers. The underflow sets TF2 flag and reloads FFFFh into the timer registers.
The EXF2 bit toggles when Timer 2 overflows or underflows according to the direction of the
count. EXF2 does not generate any interrupt. This bit can be used to provide 17-bit resolution.
17
4114B–8051–01/09
Figure 9-1.
Auto-Reload Mode Up/Down Counter (DCEN = 1)
FCLK PERIPH
:6
0
1
T2
C/T2
TR2
T2CON
T2CON
T2EX:
(DOWN COUNTING RELOAD VALUE)
if DCEN = 1, 1 = UP
FFh
FFh
if DCEN = 1, 0 = DOWN
(8-bit)
(8-bit)
if DCEN = 0, up counting
TOGGLE T2CON
EXF2
TL2
(8-bit)
TH2
(8-bit)
TF2
TIMER 2
INTERRUPT
T2CON
RCAP2L
(8-bit)
RCAP2H
(8-bit)
(UP COUNTING RELOAD VALUE)
9.2
Programmable Clock-Output
In the clock-out mode, Timer 2 operates as a 50% duty-cycle, programmable clock generator
(see Figure 9-2). The input clock increments TL2 at frequency FCLK PERIPH/2. The timer repeatedly counts to overflow from a loaded value. At overflow, the contents of RCAP2H and RCAP2L
registers are loaded into TH2 and TL2. In this mode, Timer 2 overflows do not generate interrupts. The formula gives the clock-out frequency as a function of the system oscillator frequency
and the value in the RCAP2H and RCAP2L registers:
F CLKPERIPH
Clock – OutFrequency = ---------------------------------------------------------------------------------------4 × ( 65536 – RCAP2H ⁄ RCAP2L )
For a 16 MHz system clock, Timer 2 has a programmable frequency range of 61 Hz
(FCLK PERIPH/216) to 4 MHz (FCLK PERIPH/4). The generated clock signal is brought out to T2 pin
(P1.0).
Timer 2 is programmed for the clock-out mode as follows:
• Set T2OE bit in T2MOD register.
• Clear C/T2 bit in T2CON register.
• Determine the 16-bit reload value from the formula and enter it in RCAP2H/RCAP2L
registers.
• Enter a 16-bit initial value in timer registers TH2/TL2. It can be the same as the reload value
or a different one depending on the application.
• To start the timer, set TR2 run control bit in T2CON register.
18
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
It is possible to use Timer 2 as a baud rate generator and a clock generator simultaneously. For
this configuration, the baud rates and clock frequencies are not independent since both functions use the values in the RCAP2H and RCAP2L registers.
Figure 9-2.
Clock-Out Mode C/T2 = 07
:6
FCLK PERIPH
TR2
T2CON
TL2
(8-bit)
TH2
(8-bit)
OVEFLOW
RCAP2L
(8-bit)
RCAP2H
(8-bit)
Toggle
T2
Q
D
T2OE
T2MOD
T2EX
TIMER 2
INTERRUPT
EXF2
EXEN2
T2CON
T2CON
Table 9-1.
T2CON Register
T2CON - Timer 2 Control Register (C8h)
7
6
5
4
3
2
1
0
TF2
EXF2
RCLK
TCLK
EXEN2
TR2
C/T2#
CP/RL2#
19
4114B–8051–01/09
Bit
Bit
Number
Mnemonic
7
TF2
Description
Timer 2 overflow Flag
Must be cleared by software.
Set by hardware on Timer 2 overflow, if RCLK = 0 and TCLK = 0.
6
EXF2
Timer 2 External Flag
Set when a capture or a reload is caused by a negative transition on T2EX pin if
EXEN2 = 1.
When set, causes the CPU to vector to Timer 2 interrupt routine when Timer 2 interrupt
is enabled.
Must be cleared by software. EXF2 doesn’t cause an interrupt in Up/down counter
mode (DCEN = 1)
5
RCLK
Receive Clock bit
Cleared to use timer 1 overflow as receive clock for serial port in mode 1 or 3.
Set to use Timer 2 overflow as receive clock for serial port in mode 1 or 3.
4
TCLK
Transmit Clock bit
Cleared to use timer 1 overflow as transmit clock for serial port in mode 1 or 3.
Set to use Timer 2 overflow as transmit clock for serial port in mode 1 or 3.
3
EXEN2
2
TR2
1
0
Timer 2 External Enable bit
Cleared to ignore events on T2EX pin for Timer 2 operation.
Set to cause a capture or reload when a negative transition on T2EX pin is detected, if
Timer 2 is not used to clock the serial port.
Timer 2 Run control bit
Cleared to turn off Timer 2.
Set to turn on Timer 2.
C/T2#
Timer/Counter 2 select bit
Cleared for timer operation (input from internal clock system: FCLK PERIPH).
Set for counter operation (input from T2 input pin, falling edge trigger). Must be 0 for
clock out mode.
CP/RL2#
Timer 2 Capture/Reload bit
If RCLK = 1 or TCLK = 1, CP/RL2# is ignored and timer is forced to auto-reload on
Timer 2 overflow.
Cleared to auto-reload on Timer 2 overflows or negative transitions on T2EX pin if
EXEN2 = 1.
Set to capture on negative transitions on T2EX pin if EXEN2 = 1.
Reset Value = 0000 0000b
Bit addressable
20
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 9-2.
T2MOD Register
T2MOD - Timer 2 Mode Control Register (C9h)
7
6
5
4
3
2
1
0
-
-
-
-
-
-
T2OE
DCEN
Bit
Bit
Number
Mnemonic
7
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
1
T2OE
Timer 2 Output Enable bit
Cleared to program P1.0/T2 as clock input or I/O port.
Set to program P1.0/T2 as clock output.
0
DCEN
Down Counter Enable bit
Cleared to disable Timer 2 as up/down counter.
Set to enable Timer 2 as up/down counter.
Description
Reset Value = XXXX XX00b
Not bit addressable
21
4114B–8051–01/09
10. Programmable Counter Array (PCA)
The PCA provides more timing capabilities with less CPU intervention than the standard
timer/counters. Its advantages include reduced software overhead and improved accuracy. The
PCA consists of a dedicated timer/counter which serves as the time base for an array of five
compare/capture modules. Its clock input can be programmed to count any one of the following
signals:
÷6
• Peripheral clock frequency (FCLK PERIPH) ÷ 2
• Peripheral clock frequency (FCLK PERIPH)
• Timer 0 overflow
• External input on ECI (P1.2)
Each compare/capture modules can be programmed in any one of the following modes:
• Rising and/or falling edge capture
• Software timer
• High-speed output
• Pulse width modulator
Module 4 can also be programmed as a Watchdog Timer (see Section "PCA Watchdog Timer",
page 33).
When the compare/capture modules are programmed in the capture mode, software timer, or
high-speed output mode, an interrupt can be generated when the module executes its function.
All five modules plus the PCA timer overflow share one interrupt vector.
The PCA timer/counter and compare/capture modules share Port 1 for external I/O. These pins
are listed below. If the port is not used for the PCA, it can still be used for standard I/O.
PCA Component
External I/O Pin
16-bit Counter
P1.2/ECI
16-bit Module 0
P1.3/CEX0
16-bit Module 1
P1.4/CEX1
16-bit Module 2
P1.5/CEX2
16-bit Module 3
P1.6/CEX3
The PCA timer is a common time base for all five modules (see Figure 10-1). The timer count
source is determined from the CPS1 and CPS0 bits in the CMOD register (Table 10-1) and can
be programmed to run at:
• 1/6 the peripheral clock frequency (FCLK PERIPH)
• 1/2 the peripheral clock frequency (FCLK PERIPH)
• The Timer 0 overflow
• The input on the ECI pin (P1.2)
22
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Figure 10-1. PCA Timer/Counter
To PCA
Modules
FCLK PERIPH /6
Overflow
FCLK PERIPH/2
CH
T0 OVF
It
CL
16-Bit Up/Down Counter
P1.2
CIDL
WDTE
CF
CR
CPS1
CPS0
ECF
CMOD
0xD9
CCF2
CCF1
CCF0
CCON
0xD8
Idle
CCF4 CCF3
23
4114B–8051–01/09
Table 10-1. CMOD Register
CMOD - PCA Counter Mode Register (D9h)
7
6
5
4
3
2
1
0
CIDL
WDTE
-
-
-
CPS1
CPS0
ECF
Bit
Bit
Number
Mnemonic
7
CIDL
Description
Counter Idle Control
Cleared to program the PCA Counter to continue functioning during idle Mode.
Set to program PCA to be gated off during idle.
Watchdog Timer Enable
6
WDTE
Cleared to disable Watchdog Timer function on PCA Module 4.
Set to enable Watchdog Timer function on PCA Module 4.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
CPS1
1
CPS0
PCA Count Pulse Select
CPS1CPS0
0
0
Selected PCA input
Internal clock fCLK PERIPH/6
0
Internal clock fCLK PERIPH/2
1
1
0
ECF
1
0 Timer 0 Overflow
1
External clock at ECI/P1.2 pin (max rate = fCLK PERIPH/4)
PCA Enable Counter Overflow Interrupt
Cleared to disable CF bit in CCON to inhibit an interrupt.
Set to enable CF bit in CCON to generate an interrupt.
Reset Value = 00XX X000b
Not bit addressable
The CMOD register includes three additional bits associated with the PCA (see Figure 10-4 and
Table 10-1).
• The CIDL bit which allows the PCA to stop during idle mode.
• The WDTE bit which enables or disables the watchdog function on module 4.
• The ECF bit which when set causes an interrupt and the PCA overflow flag CF (in the CCON
SFR) to be set when the PCA timer overflows.
The CCON register contains the run control bit for the PCA and the flags for the PCA timer (CF)
and each module (see Table 10-2).
• Bit CR (CCON.6) must be set by software to run the PCA. The PCA is shut off by clearing this
bit.
• Bit CF: The CF bit (CCON.7) is set when the PCA counter overflows and an interrupt will be
generated if the ECF bit in the CMOD register is set. The CF bit can only be cleared by
software.
24
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
• Bits 0 through 4 are the flags for the modules (bit 0 for module 0, bit 1 for module 1, etc.) and
are set by hardware when either a match or a capture occurs. These flags can only be
cleared by software.
Table 10-2. CCON Register
CCON - PCA Counter Control Register (D8h)
7
6
5
4
3
2
1
0
CF
CR
-
CCF4
CCF3
CCF2
CCF1
CCF0
Bit
Bit
Number
Mnemonic
7
CF
6
CR
Description
PCA Counter Overflow flag
Set by hardware when the counter rolls over. CF flags an interrupt if bit ECF in CMOD is
set. CF may be set by either hardware or software but can only be cleared by software.
PCA Counter Run control bit
Must be cleared by software to turn the PCA counter off.
Set by software to turn the PCA counter on.
5
-
4
CCF4
Reserved
The value read from this bit is indeterminate. Do not set this bit.
PCA Module 4 interrupt flag
Must be cleared by software.
Set by hardware when a match or capture occurs.
PCA Module 3 interrupt flag
3
CCF3
Must be cleared by software.
Set by hardware when a match or capture occurs.
PCA Module 2 interrupt flag
2
CCF2
Must be cleared by software.
Set by hardware when a match or capture occurs.
PCA Module 1 interrupt flag
1
CCF1
Must be cleared by software.
Set by hardware when a match or capture occurs.
PCA Module 0 interrupt flag
0
CCF0
Must be cleared by software.
Set by hardware when a match or capture occurs.
Reset Value = 000X 0000b
Not bit addressable
The watchdog timer function is implemented in module 4 (see Figure 10-4).
The PCA interrupt system is shown in Figure 10-2.
25
4114B–8051–01/09
Figure 10-2. PCA Interrupt System
CF
CR
CCF4 CCF3 CCF2 CCF1 CCF0
CCON
0xD8
PCA Timer/Counter
Module 0
Module 1
To Interrupt
Priority Decoder
Module 2
Module 3
Module 4
CMOD.0
ECF
ECCFn CCAPMn.0
IE.6
EC
IE.7
EA
PCA Modules: each one of the five compare/capture modules has six possible functions. It can
perform:
• 16-bit Capture, positive-edge triggered
• 16-bit Capture, negative-edge triggered
• 16-bit Capture, both positive and negative-edge triggered
• 16-bit Software Timer
• 16-bit High-speed Output
• 8-bit Pulse Width Modulator
In addition, module 4 can be used as a Watchdog Timer.
Each module in the PCA has a special function register associated with it. These registers are:
CCAPM0 for module 0, CCAPM1 for module 1, etc. (see Table 10-3). The registers contain the
bits that control the mode that each module will operate in.
• The ECCF bit (CCAPMn.0 where n = 0, 1, 2, 3, or 4 depending on the module) enables the
CCF flag in the CCON SFR to generate an interrupt when a match or compare occurs in the
associated module.
• PWM (CCAPMn.1) enables the pulse width modulation mode.
• The TOG bit (CCAPMn.2) when set causes the CEX output associated with the module to
toggle when there is a match between the PCA counter and the module's capture/compare
register.
• The match bit MAT (CCAPMn.3) when set will cause the CCFn bit in the CCON register to be
set when there is a match between the PCA counter and the module's capture/compare
register.
• The next two bits CAPN (CCAPMn.4) and CAPP (CCAPMn.5) determine the edge that a
capture input will be active on. The CAPN bit enables the negative edge, and the CAPP bit
enables the positive edge. If both bits are set both edges will be enabled and a capture will
occur for either transition.
• The last bit in the register ECOM (CCAPMn.6) when set enables the comparator function.
26
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 10-3 shows the CCAPMn settings for the various PCA functions.
Table 10-3. CCAPMn Registers (n = 0-4)
CCAPM0 - PCA Module 0 Compare/Capture Control Register (0DAh)
CCAPM1 - PCA Module 1 Compare/Capture Control Register (0DBh)
CCAPM2 - PCA Module 2 Compare/Capture Control Register (0DCh)
CCAPM3 - PCA Module 3 Compare/Capture Control Register (0DDh)
CCAPM4 - PCA Module 4 Compare/Capture Control Register (0DEh)
7
6
5
4
3
2
1
0
-
ECOMn
CAPPn
CAPNn
MATn
TOGn
PWMn
ECCFn
Bit
Bit
Number
Mnemonic
7
-
6
ECOMn
Description
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Enable Comparator
Cleared to disable the comparator function.
Set to enable the comparator function.
Capture Positive
5
CAPPn
4
CAPNn
3
MATn
2
TOGn
1
PWMn
Cleared to disable positive edge capture.
Set to enable positive edge capture.
Capture Negative
Cleared to disable negative edge capture.
Set to enable negative edge capture.
Match
When MATn = 1, a match of the PCA counter with this module's compare/capture
register causes the CCFn bit in CCON to be set, flagging an interrupt.
Toggle
When TOGn = 1, a match of the PCA counter with this module's compare/capture
register causes the CEXn pin to toggle.
Pulse Width Modulation Mode
Cleared to disable the CEXn pin to be used as a pulse width modulated output.
Set to enable the CEXn pin to be used as a pulse width modulated output.
Enable CCF interrupt
0
CCF0
Cleared to disable compare/capture flag CCFn in the CCON register to generate an
interrupt.
Set to enable compare/capture flag CCFn in the CCON register to generate an interrupt.
Reset Value = X000 0000b
Not bit addressable
27
4114B–8051–01/09
Table 10-4.
PCA Module Modes (CCAPMn Registers)
ECOMn
CAPPn
CAPNn
MATn
TOGn
PWMm
ECCFn
Module Function
0
0
0
0
0
0
0
No Operation
X
1
0
0
0
0
X
16-bit capture by a positive-edge
trigger on CEXn
X
0
1
0
0
0
X
16-bit capture by a negative trigger on
CEXn
X
1
1
0
0
0
X
16-bit capture by a transition on CEXn
1
0
0
1
0
0
X
16-bit Software Timer/Compare mode.
1
0
0
1
1
0
X
16-bit High-speed Output
1
0
0
0
0
1
0
8-bit PWM
1
0
0
1
X
0
X
Watchdog Timer (module 4 only)
There are two additional registers associated with each of the PCA modules. They are CCAPnH
and CCAPnL and these are the registers that store the 16-bit count when a capture occurs or a
compare should occur. When a module is used in the PWM mode these registers are used to
control the duty cycle of the output (see Table 10-5 and Table 10-6).
Table 10-5. CCAPnH Registers (n = 0-4)
CCAP0H - PCA Module 0 Compare/Capture Control Register High (0FAh)
CCAP1H - PCA Module 1 Compare/Capture Control Register High (0FBh)
CCAP2H - PCA Module 2 Compare/Capture Control Register High (0FCh)
CCAP3H - PCA Module 3 Compare/Capture Control Register High (0FDh)
CCAP4H - PCA Module 4 Compare/Capture Control Register High (0FEh)
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit
Bit
Number
Mnemonic
7-0
-
Description
PCA Module n Compare/Capture Control
CCAPnH Value
Reset Value = 0000 0000b
Not bit addressable
28
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 10-6. CCAPnL Registers (n = 0-4)
CCAP0L - PCA Module 0 Compare/Capture Control Register Low (0EAh)
CCAP1L - PCA Module 1 Compare/Capture Control Register Low (0EBh)
CCAP2L - PCA Module 2 Compare/Capture Control Register Low (0ECh)
CCAP3L - PCA Module 3 Compare/Capture Control Register Low (0EDh)
CCAP4L - PCA Module 4 Compare/Capture Control Register Low (0EEh)
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit
Bit
Number
Mnemonic
7-0
-
Description
PCA Module n Compare/Capture Control
CCAPnL Value
Reset Value = 0000 0000b
Not bit addressable
Table 10-7. CH Register
CH - PCA Counter Register High (0F9h)
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit
Bit
Number
Mnemonic
Description
7-0
-
PCA counter
CH Value
Reset Value = 0000 0000b
Not bit addressable
Table 10-8. CL Register
CL - PCA Counter Register Low (0E9h)
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Bit
Bit
Number
Mnemonic
7-0
-
Description
PCA Counter
CL Value
Reset Value = 0000 0000b
Not bit addressable
29
4114B–8051–01/09
10.1
PCA Capture Mode
To use one of the PCA modules in the capture mode either one or both of the CCAPM bits
CAPN and CAPP for that module must be set. The external CEX input for the module (on port 1)
is sampled for a transition. When a valid transition occurs the PCA hardware loads the value of
the PCA counter registers (CH and CL) into the module's capture registers (CCAPnL and CCAPnH). If the CCFn bit for the module in the CCON SFR and the ECCFn bit in the CCAPMn SFR
are set then an interrupt will be generated (see Figure 10-3).
Figure 10-3. PCA Capture Mode
CF
CR
CCF4 CCF3 CCF2
CCF1 CCF0 CCON
0xD8
PCA IT
PCA Counter/Timer
Cex.n
CH
CL
CCAPnH
CCAPnL
Capture
ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn CCAPMn, n= 0 to 4
0xDA to 0xDE
10.2
16-bit Software Timer/ Compare Mode
The PCA modules can be used as software timers by setting both the ECOM and MAT bits in
the modules CCAPMn register. The PCA timer will be compared to the module's capture registers and when a match occurs an interrupt will occur if the CCFn (CCON SFR) and the ECCFn
(CCAPMn SFR) bits for the module are both set (see Figure 10-4).
30
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Figure 10-4. PCA Compare Mode and PCA Watchdog Timer
CCON
CF
Write to
CCAPnL
CR
CCF4 CCF3 CCF2 CCF1 CCF0
0xD8
Reset
PCA IT
Write t o
CCAPnH
1
CCAPnH
0
CCAPnL
Enable
Match
16 bit comparator
CH
RESET *
CL
PCA counter/timer
ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn
CIDL
WDTE
CPS1 CPS0
ECF
CCAPMn, n = 0 to 4
0xDA to 0xDE
CMOD
0xD9
Before enabling ECOM bit, CCAPnL and CCAPnH should be set with a non zero value, otherwise an unwanted match could happen. Writing to CCAPnH will set the ECOM bit.
Once ECOM set, writing CCAPnL will clear ECOM so that an unwanted match doesn’t occur
while modifying the compare value. Writing to CCAPnH will set ECOM. For this reason, user
software should write CCAPnL first, and then CCAPnH. Of course, the ECOM bit can still be
controlled by accessing to CCAPMn register.
10.3
High-speed Output Mode
In this mode, the CEX output (on port 1) associated with the PCA module will toggle each time a
match occurs between the PCA counter and the module's capture registers. To activate this
mode the TOG, MAT, and ECOM bits in the module's CCAPMn SFR must be set (see
Figure 10-5).
A prior write must be done to CCAPnL and CCAPnH before writing the ECOMn bit.
31
4114B–8051–01/09
Figure 10-5. PCA High-speed Output Mode
CF
CR
CCF4 CCF3 CCF2 CCF1 CCF0
CCON
0xD8
Write to
CCA PnL Reset
PCA IT
Write to
CCAPnH
1
CCAPnH
0
CCAPnL
Enable
16 bit comparator
CH
Match
CL
CEXn
PCA counter/timer
ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn
CCAPMn, n = 0 to 4
0xDA to 0xDE
Before enabling ECOM bit, CCAPnL and CCAPnH should be set with a non zero value, otherwise an unwanted match could occur.
Once ECOM is set, writing CCAPnL will clear ECOM so that an unwanted match doesn’t occur
while modifying the compare value. Writing to CCAPnH will set ECOM. For this reason, user
software should write CCAPnL first, and then CCAPnH. Of course, the ECOM bit can still be
controlled by accessing the CCAPMn register.
10.4
Pulse Width Modulator Mode
All of the PCA modules can be used as PWM outputs. Figure 10-6 shows the PWM function.
The frequency of the output depends on the source for the PCA timer. All of the modules will
have the same frequency of output because they all share the PCA timer. The duty cycle of each
module is independently variable using the module's capture register CCAPLn. When the value
of the PCA CL SFR is less than the value in the module's CCAPLn SFR the output will be low,
when it is equal to or greater than the output will be high. When CL overflows from FF to 00,
CCAPLn is reloaded with the value in CCAPHn. This allows updating the PWM without glitches.
The PWM and ECOM bits in the module's CCAPMn register must be set to enable the PWM
mode.
32
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Figure 10-6. PCA PWM Mode
CCAPnH
Overflow
CCAPnL
“0”
CEXn
Enable
8-Bit Comparator
“1”
CL
PCA Counter/Timer
ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn
CCAPMn, n= 0 to 4
0xDA to 0xDE
10.5
PCA Watchdog Timer
An on-board watchdog timer is available with the PCA to improve the reliability of the system
without increasing chip count. Watchdog timers are useful for systems that are susceptible to
noise, power glitches, or electrostatic discharge. Module 4 is the only PCA module that can be
programmed as a watchdog. However, this module can still be used for other modes if the
watchdog is not needed. Figure 10-4 shows a diagram of how the watchdog works. The user
pre-loads a 16-bit value in the compare registers. Just like the other compare modes, this 16-bit
value is compared to the PCA timer value. If a match is allowed to occur, an internal reset will be
generated. This will not cause the RST pin to be driven high.
In order to hold off the reset, the user has three options:
1. Periodically change the compare value so it will never match the PCA timer.
2. Periodically change the PCA timer value so it will never match the compare values.
3. Disable the watchdog by clearing the WDTE bit before a match occurs and then reenable it.
The first two options are more reliable because the watchdog timer is never disabled as in option
#3. If the program counter ever goes astray, a match will eventually occur and cause an internal
reset. The second option is also not recommended if other PCA modules are being used.
Remember, the PCA timer is the time base for all modules; changing the time base for other
modules would not be a good idea. Thus, in most applications the first solution is the best option.
This watchdog timer won’t generate a reset out on the reset pin.
33
4114B–8051–01/09
AT83C51RB2/RC2
12. Interrupt System
The AT83C51RB2/RC2 have a total of 8 interrupt vectors: two external interrupts (INT0 and
INT1), three timer interrupts (timers 0, 1 and 2), the serial port interrupt, Keyboard interrupt and
the PCA global interrupt. These interrupts are shown in Figure 12-1.
Figure 12-1. Interrupt Control System
High Priority
Interrupt
IPH, IPL
3
INT0
IE0
0
3
TF0
0
3
INT1
IE1
0
3
Interrupt
Polling
Sequence, Decreasing from
High to Low Priority
TF1
0
3
PCA IT
0
RI
TI
3
TF2
EXF2
3
0
0
3
KBD IT
0
Individual Enable
Global Disable
Low Priority
Interrupt
Each of the interrupt sources can be individually enabled or disabled by setting or clearing a bit
in the Interrupt Enable register (Table 12-5 and Table 12-3). This register also contains a global
disable bit, which must be cleared to disable all interrupts at once.
Each interrupt source also can be individually programmed to one out of four priority levels by
setting or clearing a bit in the Interrupt Priority register (Table 12-6) and in the Interrupt Priority
High register (Table 12-4 and Table 12-5) shows the bit values and priority levels associated
with each combination.
12.1
Registers
The PCA interrupt vector is located at address 0033H, the Keyboard interrupt vector is located
at address 004BH. All other vectors addresses are the same as standard C52 devices.
45
4114B–8051–01/09
Table 12-1.
Priority Level Bit Values
IPH.x
IPL.x
Interrupt Level Priority
0
0
0 (Lowest)
0
1
1
1
0
2
1
1
3 (Highest)
A low-priority interrupt can be interrupted by a high priority interrupt, but not by another low-priority interrupt. A high-priority interrupt can’t be interrupted by any other interrupt source.
If two interrupt requests of different priority levels are received simultaneously, the request of
higher priority level is serviced. If interrupt requests of the same priority level are received simultaneously, an internal polling sequence determines which request is serviced. Thus within each
priority level there is a second priority structure determined by the polling sequence.
Table 12-2. IEO Register
IE0 - Interrupt Enable Register (A8h)
7
6
5
4
3
2
1
0
EA
EC
ET2
ES
ET1
EX1
ET0
EX0
Bit
Number
Bit
Mnemonic Description
7
EA
6
EC
Enable All interrupt bit
Cleared to disable all interrupts.
Set to enable all interrupts.
PCA interrupt enable bit
Cleared to disable.
Set to enable.
46
5
ET2
Timer 2 overflow interrupt enable bit
Cleared to disable Timer 2 overflow interrupt.
Set to enable Timer 2 overflow interrupt.
4
ES
Serial port enable bit
Cleared to disable serial port interrupt.
Set to enable serial port interrupt.
3
ET1
Timer 1 overflow interrupt enable bit
Cleared to disable timer 1 overflow interrupt.
Set to enable timer 1 overflow interrupt.
2
EX1
External interrupt 1 enable bit
Cleared to disable external interrupt 1.
Set to enable external interrupt 1.
1
ET0
Timer 0 overflow interrupt enable bit
Cleared to disable timer 0 overflow interrupt.
Set to enable timer 0 overflow interrupt.
0
EX0
External interrupt 0 enable bit
Cleared to disable external interrupt 0.
Set to enable external interrupt 0.
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Reset Value = 0000 0000b
Bit addressable
Table 12-3. IPL0 Register
IPL0 - Interrupt Priority Register (B8h)
7
6
5
4
3
2
1
0
-
PPCL
PT2L
PSL
PT1L
PX1L
PT0L
PX0L
Bit
Number
Bit
Mnemonic Description
Reserved
The value read from this bit is indeterminate. Do not set this bit.
7
-
6
PPCL
PCA interrupt priority bit
Refer to PPCH for priority level.
5
PT2L
Timer 2 overflow interrupt priority bit
Refer to PT2H for priority level.
4
PSL
Serial port priority bit
Refer to PSH for priority level.
3
PT1L
Timer 1 overflow interrupt priority bit
Refer to PT1H for priority level.
2
PX1L
External interrupt 1 priority bit
Refer to PX1H for priority level.
1
PT0L
Timer 0 overflow interrupt priority bit
Refer to PT0H for priority level.
0
PX0L
External interrupt 0 priority bit
Refer to PX0H for priority level.
Reset Value = X000 0000b
Bit addressable
Table 12-4. IPH0 Register
IPH0 - Interrupt Priority High Register (B7h)
7
6
5
4
3
2
1
0
-
PPCH
PT2H
PSH
PT1H
PX1H
PT0H
PX0H
47
4114B–8051–01/09
Bit
Number
7
6
5
4
3
2
1
0
Bit
Mnemonic Description
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
PPCH
PCA interrupt priority high bit.
PPCHPPCLPriority Level
0 0Lowest
0 1
1 0
1 1Highest
PT2H
Timer 2 overflow interrupt priority high bit
PT2HPT2LPriority Level
0 0Lowest
0 1
1 0
1 1Highest
PSH
Serial port priority high bit
PSH PSLPriority Level
0 0Lowest
0 1
1 0
1 1Highest
PT1H
Timer 1 overflow interrupt priority high bit
PT1HPT1LPriority Level
0 0 Lowest
0 1
1 0
1 1Highest
PX1H
External interrupt 1 priority high bit
PX1HPX1LPriority Level
0 0Lowest
0 1
1 0
1 1Highest
PT0H
Timer 0 overflow interrupt priority high bit
PT0HPT0LPriority Level
0 0Lowest
0 1
1 0
1 1Highest
PX0H
External interrupt 0 priority high bit
PX0H PX0LPriority Level
0 0Lowest
0 1
1 0
1 1Highest
Reset Value = X000 0000b
Not bit addressable
Table 12-5. IE1 Register
IE1 - Interrupt Enable Register (B1h)
48
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
KBD
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Bit
Number
Bit
Mnemonic Description
7
-
Reserved
6
-
Reserved
5
-
Reserved
4
-
Reserved
3
-
Reserved
2
-
Reserved
1
-
Reserved
0
KBD
Keyboard interrupt Enable bit
Cleared to disable keyboard interrupt.
Set to enable keyboard interrupt.
Reset Value = XXXX XXX0b
Bit addressable
Table 12-6. IPL1 Register
IPL1 - Interrupt Priority Register (B2h)
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
KBDL
Bit
Number
Bit
Mnemonic Description
7
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
1
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
0
KBDL
Keyboard Interrupt Priority bit
Refer to KBDH for priority level.
Reset Value = XXXX XXX0b
Bit addressable
Table 12-7.
IPH1 Register
49
4114B–8051–01/09
IPH1 - Interrupt Priority High Register (B3h)
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
KBDH
Bit
Number
Bit
Mnemonic Description
7
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
3
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
2
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
1
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
0
Keyboard interrupt Priority High bit
KB DHKBDLPriority Level
0 0 Lowest
0 1
1 0
1 1Highest
KBDH
Reset Value = XXXX XXX0b
Not bit addressable
12.2
Interrupt Sources and Vector Addresses
Table 12-8.
50
Interrupt Sources and Vector Addresses
Interrupt
Request
Vector
Number
Polling Priority
Interrupt Source
Address
0
0
Reset
1
1
INT0
IE0
0003h
2
2
Timer 0
TF0
000Bh
3
3
INT1
IE1
0013h
4
4
Timer 1
IF1
001Bh
5
6
UART
RI+TI
0023h
6
7
Timer 2
TF2+EXF2
002Bh
7
5
PCA
CF + CCFn (n = 0-4)
0033h
8
8
Keyboard
KBDIT
003Bh
0000h
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
51
4114B–8051–01/09
11. Serial I/O Port
The serial I/O port in the AT83C51RB2/RC2 is compatible with the serial I/O port in the 80C52.
It provides both synchronous and asynchronous communication modes. It operates as a Universal Asynchronous Receiver and Transmitter (UART) in three full-duplex modes (Modes 1, 2 and
3). Asynchronous transmission and reception can occur simultaneously and at different baud
rates
Serial I/O port includes the following enhancements:
• Framing error detection
• Automatic address recognition
11.1
Framing Error Detection
Framing bit error detection is provided for the three asynchronous modes (modes 1, 2 and 3). To
enable the framing bit error detection feature, set SMOD0 bit in PCON register (see Figure 111).
Figure 11-1. Framing Error Block diagram
SM 0/FE
SM 1
SM 2
RE N
TB8
RB8
TI
RI
S CO N (9 8h )
Se t FE bit if stop bit is 0 (fram ing erro r) (SM OD0 = 1)
SM 0 to UA RT m o de con tro l (SM OD0 = 0 )
SM OD1
1SM OD0
-
PO F
GF1
GF0
PD
IDL
PCON (87 h)
To UA RT fra min g e rro r co nt ro l
When this feature is enabled, the receiver checks each incoming data frame for a valid stop bit.
An invalid stop bit may result from noise on the serial lines or from simultaneous transmission by
two CPUs. If a valid stop bit is not found, the Framing Error bit (FE) in SCON register (see Table
11-4) bit is set.
Software may examine FE bit after each reception to check for data errors. Once set, only software or a reset can clear FE bit. Subsequently, received frames with valid stop bits cannot clear
FE bit. When FE feature is enabled, RI rises on stop bit instead of the last data bit (see Figure
11-2 and Figure 11-3).
Figure 11-2. UART Timings in Mode 1
RXD
D0
Start
bit
D1
D2
D3
D4
Data byte
D5
D6
D7
Stop
bit
RI
SMOD0=X
FE
SMOD0=1
34
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Figure 11-3. UART Timings in Modes 2 and 3
RXD
D0
.Start
Bit
D1
D2
D3
D4
D5
Data Byte
D6
D7
D8
Ninth Stop
Bit Bit
RI
SMOD0 = 0
RI
SMOD0 = 1
FE
SMOD0 = 1
11.2
Automatic Address Recognition
The automatic address recognition feature is enabled when the multiprocessor communication
feature is enabled (SM2 bit in SCON register is set).
Implemented in hardware, automatic address recognition enhances the multiprocessor communication feature by allowing the serial port to examine the address of each incoming command
frame. Only when the serial port recognizes its own address, the receiver sets RI bit in SCON
register to generate an interrupt. This ensures that the CPU is not interrupted by command
frames addressed to other devices.
If desired, you may enable the automatic address recognition feature in mode 1. In this configuration, the stop bit takes the place of the ninth data bit. Bit RI is set only when the received
command frame address matches the device’s address and is terminated by a valid stop bit.
To support automatic address recognition, a device is identified by a given address and a broadcast address.
Note:
11.2.1
The multiprocessor communication and automatic address recognition features cannot be
enabled in mode 0 (i.e. setting SM2 bit in SCON register in mode 0 has no effect).
Given Address
Each device has an individual address that is specified in SADDR register; the SADEN register
is a mask byte that contains don’t care bits (defined by zeros) to form the device’s given
address. The don’t care bits provide the flexibility to address one or more slaves at a time. The
following example illustrates how a given address is formed.
To address a device by its individual address, the SADEN mask byte must be 1111 1111b.
For example:
SADDR0101 0110b
SADEN1111 1100b
Given0101 01XXb
The following is an example of how to use given addresses to address different slaves:
Slave A:SADDR1111 0001b
SADEN1111 1010b
Given1111 0X0Xb
Slave B:SADDR1111 0011b
SADEN1111 1001b
35
4114B–8051–01/09
Given1111 0XX1b
Slave C:SADDR1111 0010b
SADEN1111 1101b
Given1111 00X1b
The SADEN byte is selected so that each slave may be addressed separately.
For slave A, bit 0 (the LSB) is a don’t-care bit; for slaves B and C, bit 0 is a 1. To communicate
with slave A only, the master must send an address where bit 0 is clear (e.g. 1111 0000b).
For slave A, bit 1 is a 1; for slaves B and C, bit 1 is a don’t care bit. To communicate with slaves
B and C, but not slave A, the master must send an address with bits 0 and 1 both set (e.g. 1111
0011b).
To communicate with slaves A, B and C, the master must send an address with bit 0 set, bit 1
clear, and bit 2 clear (e.g. 1111 0001b).
11.2.2
Broadcast Address
A broadcast address is formed from the logical OR of the SADDR and SADEN registers with
zeros defined as don’t-care bits, e.g.:
SADDR0101 0110b
SADEN1111 1100b
Broadcast
= SADDR OR SADEN1111 111Xb
The use of don’t-care bits provides flexibility in defining the broadcast address, however in most
applications, a broadcast address is FFh. The following is an example of using broadcast
addresses:
Slave A:SADDR1111 0001b
SADEN1111 1010b
Broadcast1111 1X11b,
Slave B:SADDR1111 0011b
SADEN1111 1001b
Broadcast1111 1X11B,
Slave C:SADDR = 1111 0010b
SADEN1111 1101b
Broadcast1111 1111b
For slaves A and B, bit 2 is a don’t care bit; for slave C, bit 2 is set. To communicate with all of
the slaves, the master must send an address FFh. To communicate with slaves A and B, but not
slave C, the master can send and address FBh.
36
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
11.2.3
Reset Addresses
On reset, the SADDR and SADEN registers are initialized to 00h, i.e. the given and broadcast
addresses are XXXX XXXXb (all don’t-care bits). This ensures that the serial port will reply to any
address, and so, that it is backwards compatible with the 80C51 microcontrollers that do not
support automatic address recognition.
Table 11-1.
7
SADEN Register
SADEN - Slave Address Mask Register (B9h)
6
5
4
3
2
1
0
4
3
2
1
0
Reset Value = 0000 0000b
Not bit addressable
Table 11-2. SADDR Register
SADDR - Slave Address Register (A9h)
7
6
5
Reset Value = 0000 0000b
Not bit addressable
11.3
Baud Rate Selection for UART for Mode 1 and 3
The Baud Rate Generator for transmit and receive clocks can be selected separately via the
T2CON and BDRCON registers.
Figure 11-4. Baud Rate selection
TIMER1
TIMER2
0
TI MER_BRG_RX
1
0
/ 16
1
Rx Clock
RCLK
RBCK
INT_BRG
TIMER1
0
TI MER2
1
TIMER_BRG_TX
0
1
/ 16
Tx Clock
TCLK
INT_BRG
TBCK
37
4114B–8051–01/09
Table 11-3.
11.3.1
Baud Rate Selection Table UART
TCLK
RCLK
TBCK
RBCK
Clock Source
Clock Source
(T2CON)
(T2CON)
(BDRCON)
(BDRCON)
UART Tx
UART Rx
0
0
0
0
Timer 1
Timer 1
1
0
0
0
Timer 2
Timer 1
0
1
0
0
Timer 1
Timer 2
1
1
0
0
Timer 2
Timer 2
X
0
1
0
INT_BRG
Timer 1
X
1
1
0
INT_BRG
Timer 2
0
X
0
1
Timer 1
INT_BRG
1
X
0
1
Timer 2
INT_BRG
X
X
1
1
INT_BRG
INT_BRG
Internal Baud Rate Generator (BRG)
When the internal Baud Rate Generator is used, the Baud Rates are determined by the BRG
overflow depending on the BRL reload value, the value of SPD bit (Speed Mode) in BDRCON
register and the value of the SMOD1 bit in PCON register.
Figure 11-5. Internal Baud Rate
auto reload counter
Peripheral clock
/6
0
overflow
/2
BRG
1
SPD
0
INT_BRG
1
BRL
BRR
• The baud rate for UART is token by formula:
2 SMOD × F CLKPERIPH
BaudRate = --------------------------------------------------------------------------------------------------------2 × 2 × 6 〈 1 – SPD〉 × 16 × [ 256 – ( BRL ) ]
2 SMOD1 × F CLKPERIPH
( BRL ) = 256 – ---------------------------------------------------------------------------------------2 × 2 × 6 ( 1 – SPD ) × 16 × BaudRate
38
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 11-4. SCON Register
SCON - Serial Control Register (98h)
7
6
5
4
3
2
1
0
FE/SM0
SM1
SM2
REN
TB8
RB8
TI
RI
Bit
Bit
Number
Mnemonic
Description
Framing Error bit (SMOD0 = 1)
7
FE
Clear to reset the error state, not cleared by a valid stop bit.
Set by hardware when an invalid stop bit is detected.
SMOD0 must be set to enable access to the FE bit
SM0
Serial port Mode bit 0
Refer to SM1 for serial port mode selection.
SMOD0 must be cleared to enable access to the SM0 bit
Serial port Mode bit 1
SM1ModeDescriptionBaud Rate
6
SM1
0
0Shift RegisterfCPU PERIPH/6
1
18-bit UARTVariable
0
29-bit UARTfCPU PERIPH /32 or /16
1
39-bit UARTVariable
Serial port Mode 2 bit/Multiprocessor Communication Enable bit
5
SM2
4
REN
3
TB8
Clear to disable multiprocessor communication feature.
Set to enable multiprocessor communication feature in mode 2 and 3, and eventually
mode 1. This bit should be cleared in mode 0.
Reception Enable bit
Clear to disable serial reception.
Set to enable serial reception.
Transmitter Bit 8/Ninth bit to transmit in modes 2 and 3
2
RB8
o transmit a logic 0 in the 9th bit.
Set to transmit a logic 1 in the 9th bit.
Receiver Bit 8/Ninth bit received in modes 2 and 3
Cleared by hardware if 9th bit received is a logic 0.
Set by hardware if 9th bit received is a logic 1.
In mode 1, if SM2=0, RB8 is the received stop bit. In mode 0 RB8 is not used.
1
0
TI
Transmit Interrupt flag
Clear to acknowledge interrupt.
Set by hardware at the end of the 8th bit time in mode 0 or at the beginning of the stop
bit in the other modes.
RI
Receive Interrupt flag
Clear to acknowledge interrupt.
Set by hardware at the end of the 8th bit time in mode 0, see Figure 11-2. and Figure
11-3. in the other modes.
Reset Value = 0000 0000b
Bit addressable
39
4114B–8051–01/09
Table 11-5.
Example of Computed Value when X2 = 1, SMOD1 = 1, SPD = 1
Baud Rates
FOSC=16.384 MHz
FOSC=24 MHz
BRL
Error (%)
BRL
Error (%)
115200
247
1.23
243
0.16
57600
238
1.23
230
0.16
38400
229
1.23
217
0.16
28800
220
1.23
204
0.16
19200
203
0.63
178
0.16
9600
149
0.31
100
0.16
4800
43
1.23
-
-
Table 11-6.
Example of Computed Value when X2 = 0, SMOD1 = 0, SPD = 0
Baud Rates
FOSC=16.384 MHz
FOSC=24 MHz
BRL
Error (%)
BRL
Error (%)
4800
247
1.23
243
0.16
2400
238
1.23
230
0.16
1200
220
1.23
202
3.55
600
185
0.16
152
0.16
The baud rate generator can be used for mode 1 or 3 (see Figure 11-4.), but also for mode 0 for
UART, thanks to the bit SRC located in BDRCON register (Table 11-13.)
11.4
UART Registers
Table 11-7. SADEN Register
SADEN - Slave Address Mask Register for UART (B9h)
7
6
5
4
3
2
1
0
3
2
1
0
Reset Value = 0000 0000b
Table 11-8. SADDR Register
SADDR - Slave Address Register for UART (A9h)
7
6
5
4
Reset Value = 0000 0000b
40
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 11-9. SBUF Register
SBUF - Serial Buffer Register for UART (99h)
7
6
5
4
3
2
1
0
Reset Value = XXXX XXXXb
Table 11-10. BRL Register
BRL - Baud Rate Reload Register for the internal baud rate generator, UART (9Ah)
7
6
5
4
3
2
1
0
Reset Value = 0000 0000b
41
4114B–8051–01/09
Table 11-11. T2CON Register
T2CON - Timer 2 Control Register (C8h)
7
6
5
4
3
2
1
0
TF2
EXF2
RCLK
TCLK
EXEN2
TR2
C/T2#
CP/RL2#
Bit
Bit
Number
Mnemonic
7
TF2
Description
Timer 2 overflow Flag
Must be cleared by software.
Set by hardware on Timer 2 overflow, if RCLK=0 and TCLK=0.
6
EXF2
Timer 2 External Flag
Set when a capture or a reload is caused by a negative transition on T2EX pin if EXEN2
= 1.
When set, causes the CPU to vector to Timer 2 interrupt routine when Timer 2 interrupt
is enabled.
Must be cleared by software. EXF2 doesn’t cause an interrupt in Up/down counter
mode (DCEN=1)
5
RCLK
Receive Clock bit for UART
Cleared to use timer 1 overflow as receive clock for serial port in mode 1 or 3.
Set to use Timer 2 overflow as receive clock for serial port in mode 1 or 3.
4
TCLK
Transmit Clock bit for UART
Cleared to use timer 1 overflow as transmit clock for serial port in mode 1 or 3.
Set to use Timer 2 overflow as transmit clock for serial port in mode 1 or 3.
3
EXEN2
2
TR2
1
0
Timer 2 External Enable bit
Cleared to ignore events on T2EX pin for Timer 2 operation.
Set to cause a capture or reload when a negative transition on T2EX pin is detected, if
Timer 2 is not used to clock the serial port.
Timer 2 Run control bit
Cleared to turn off Timer 2.
Set to turn on Timer 2.
C/T2#
Timer/Counter 2 select bit
Cleared for timer operation (input from internal clock system: FCLK PERIPH).
Set for counter operation (input from T2 input pin, falling edge trigger). Must be 0 for
clock out mode.
CP/RL2#
Timer 2 Capture/Reload bit
If RCLK = 1 or TCLK = 1, CP/RL2# is ignored and timer is forced to auto-reload on
Timer 2 overflow.
Cleared to auto-reload on Timer 2 overflows or negative transitions on T2EX pin if
EXEN2 = 1.
Set to capture on negative transitions on T2EX pin if EXEN2 = 1.
Reset Value = 0000 0000b
Bit addressable
42
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 11-12. PCON Register
PCON - Power Control Register (87h)
7
6
5
4
3
2
1
0
SMOD1
SMOD0
-
POF
GF1
GF0
PD
IDL
Bit
Bit
Number
Mnemonic
7
SMOD1
6
SMOD0
5
-
4
POF
Power-off Flag
Cleared to recognize next reset type.
Set by hardware when VCC rises from 0 to its nominal voltage. Can also be set by
software.
3
GF1
General purpose Flag
Cleared by user for general purpose usage.
Set by user for general purpose usage.
2
GF0
General purpose Flag
Cleared by user for general purpose usage.
Set by user for general purpose usage.
1
PD
Power-down mode bit
Cleared by hardware when reset occurs.
Set to enter power-down mode.
0
IDL
Idle mode bit
Cleared by hardware when interrupt or reset occurs.
Set to enter idle mode.
Description
Serial Port Mode bit 1 for UART
Set to select double baud rate in mode 1, 2 or 3.
Serial Port Mode bit 0 for UART
Cleared to select SM0 bit in SCON register.
Set to select FE bit in SCON register.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reset Value = 00X1 0000b
Not bit addressable
Power-off flag reset value will be 1 only after a power on (cold reset). A warm reset doesn’t affect
the value of this bit.
43
4114B–8051–01/09
Table 11-13. BDRCON Register
BDRCON - Baud Rate Control Register (9Bh)
7
6
5
4
3
2
1
0
-
-
-
BRR
TBCK
RBCK
SPD
SRC
Bit
Number
Bit
Mnemonic
7
-
Reserved
The value read from this bit is indeterminate. Do not set this bit
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
BRR
Baud Rate Run Control bit
Cleared to stop the internal Baud Rate Generator.
Set to start the internal Baud Rate Generator.
3
TBCK
Transmission Baud rate Generator Selection bit for UART
Cleared to select Timer 1 or Timer 2 for the Baud Rate Generator.
Set to select internal Baud Rate Generator.
2
RBCK
Reception Baud Rate Generator Selection bit for UART
Cleared to select Timer 1 or Timer 2 for the Baud Rate Generator.
Set to select internal Baud Rate Generator.
1
SPD
0
SRC
Description
Baud Rate Speed Control bit for UART
Cleared to select the SLOW Baud Rate Generator.
Set to select the FAST Baud Rate Generator.
Baud Rate Source select bit in Mode 0 for UART
Cleared to select FOSC/12 as the Baud Rate Generator (FCLK PERIPH/6 in X2 mode).
Set to select the internal Baud Rate Generator for UARTs in mode 0.
Reset Value = XXX0 0000b
Not bit addressable
44
AT83C51RB2/RC2
4114B–8051–01/09
13. Keyboard Interface
The AT83C51RB2/RC2 implement a keyboard interface allowing the connection of a 8 x n
matrix keyboard. It is based on 8 inputs with programmable interrupt capability on both high or
low level. These inputs are available as alternate function of P1 and allow to exit from idle and
power-down modes.
The keyboard interfaces with the C51 core through 3 special function registers: KBLS, the Keyboard Level Selection register (Table 13-3), KBE, The Keyboard Interrupt Enable register
(Table 13-2), and KBF, the Keyboard Flag register (Table 13-1).
13.0.1
Interrupt
The keyboard inputs are considered as 8 independent interrupt sources sharing the same interrupt vector. An interrupt enable bit (KBD in IE1) allows global enable or disable of the keyboard
interrupt (see Figure 13-1). As detailed in Figure 13-2 each keyboard input has the capability to
detect a programmable level according to KBLS.x bit value. Level detection is then reported in
interrupt flags KBF.x that can be masked by software using KBE.x bits.
This structure allow keyboard arrangement from 1 x n to 8 x n matrix and allows usage of P1
inputs for other purpose.
Figure 13-1. Keyboard Interface Block Diagram
VCC
0
P1:x
KBF.x
1
Internal Pull-up
KBE.x
KBLS.x
Figure 13-2. Keyboard Input Circuitry
P1.0
Input Circuitry
P1.1
Input Circuitry
P1.2
Input Circuitry
P1.3
Input Circuitry
P1.4
Input Circuitry
P1.5
Input Circuitry
P1.6
Input Circuitry
P1.7
Input Circuitry
KBDIT
13.0.2
52
KBD
IE1
Keyboard Interface
Interrupt Request
Power Reduction Mode
P1 inputs allow exit from idle and power-down modes as detailed in Section “Power-down
Mode”, page 56.
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
13.1
Registers
Table 13-1. KBF Register
KBF - Keyboard Flag Register (9Eh)
7
6
5
4
3
2
1
0
KBF7
KBF6
KBF5
KBF4
KBF3
KBF2
KBF1
KBF0
Bit
Number
Bit
Mnemonic Description
7
KBF7
Keyboard line 7 flag
Set by hardware when the Port line 7 detects a programmed level. It generates a
Keyboard interrupt request if the KBKBIE.7 bit in KBIE register is set.
Must be cleared by software.
6
KBF6
Keyboard line 6 flag
Set by hardware when the Port line 6 detects a programmed level. It generates a
Keyboard interrupt request if the KBIE.6 bit in KBIE register is set.
Must be cleared by software.
5
KBF5
Keyboard line 5 flag
Set by hardware when the Port line 5 detects a programmed level. It generates a
Keyboard interrupt request if the KBIE.5 bit in KBIE register is set.
Must be cleared by software.
4
KBF4
Keyboard line 4 flag
Set by hardware when the Port line 4 detects a programmed level. It generates a
Keyboard interrupt request if the KBIE.4 bit in KBIE register is set.
Must be cleared by software.
3
KBF3
Keyboard line 3 flag
Set by hardware when the Port line 3 detects a programmed level. It generates a
Keyboard interrupt request if the KBIE.3 bit in KBIE register is set.
Must be cleared by software.
2
KBF2
Keyboard line 2 flag
Set by hardware when the Port line 2 detects a programmed level. It generates a
Keyboard interrupt request if the KBIE.2 bit in KBIE register is set.
Must be cleared by software.
1
KBF1
Keyboard line 1 flag
Set by hardware when the Port line 1 detects a programmed level. It generates a
Keyboard interrupt request if the KBIE.1 bit in KBIE register is set.
Must be cleared by software.
0
KBF0
Keyboard line 0 flag
Set by hardware when the Port line 0 detects a programmed level. It generates a
Keyboard interrupt request if the KBIE.0 bit in KBIE register is set.
Must be cleared by software.
Reset Value = 0000 0000b
53
4114B–8051–01/09
Table 13-2. KBE Register
KBE - Keyboard Input Enable Register (9Dh)
7
6
5
4
3
2
1
0
KBE7
KBE6
KBE5
KBE4
KBE3
KBE2
KBE1
KBE0
Bit
Number
Bit
Mnemonic Description
7
KBE7
Keyboard line 7 enable bit
Cleared to enable standard I/O pin.
Set to enable KBF.7 bit in KBF register to generate an interrupt request.
6
KBE6
Keyboard line 6 enable bit
Cleared to enable standard I/O pin.
Set to enable KBF.6 bit in KBF register to generate an interrupt request.
5
KBE5
Keyboard line 5 enable bit
Cleared to enable standard I/O pin.
Set to enable KBF.5 bit in KBF register to generate an interrupt request.
4
KBE4
Keyboard line 4 enable bit
Cleared to enable standard I/O pin.
Set to enable KBF.4 bit in KBF register to generate an interrupt request.
3
KBE3
Keyboard line 3 enable bit
Cleared to enable standard I/O pin.
Set to enable KBF.3 bit in KBF register to generate an interrupt request.
2
KBE2
Keyboard line 2 enable bit
Cleared to enable standard I/O pin.
Set to enable KBF.2 bit in KBF register to generate an interrupt request.
1
KBE1
Keyboard line 1 enable bit
Cleared to enable standard I/O pin.
Set to enable KBF.1 bit in KBF register to generate an interrupt request.
0
KBE0
Keyboard line 0 enable bit
Cleared to enable standard I/O pin.
Set to enable KBF.0 bit in KBF register to generate an interrupt request.
Reset Value = 0000 0000b
54
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 13-3. KBLS Register
KBLS - Keyboard Level Selector Register (9Ch)
7
6
5
4
3
2
1
0
KBLS7
KBLS6
KBLS5
KBLS4
KBLS3
KBLS2
KBLS1
KBLS0
Bit
Number
Bit
Mnemonic Description
7
KBLS7
Keyboard line 7 level selection bit
Cleared to enable a low level detection on Port line 7.
Set to enable a high level detection on Port line 7.
6
KBLS6
Keyboard line 6 level selection bit
Cleared to enable a low level detection on Port line 6.
Set to enable a high level detection on Port line 6.
5
KBLS5
Keyboard line 5 level selection bit
Cleared to enable a low level detection on Port line 5.
Set to enable a high level detection on Port line 5.
4
KBLS4
Keyboard line 4 level selection bit
Cleared to enable a low level detection on Port line 4.
Set to enable a high level detection on Port line 4.
3
KBLS3
Keyboard line 3 level selection bit
Cleared to enable a low level detection on Port line 3.
Set to enable a high level detection on Port line 3.
2
KBLS2
Keyboard line 2 level selection bit
Cleared to enable a low level detection on Port line 2.
Set to enable a high level detection on Port line 2.
1
KBLS1
Keyboard line 1 level selection bit
Cleared to enable a low level detection on Port line 1.
Set to enable a high level detection on Port line 1.
0
KBLS0
Keyboard line 0 level selection bit
Cleared to enable a low level detection on Port line 0.
Set to enable a high level detection on Port line 0.
Reset Value = 0000 0000b
55
4114B–8051–01/09
14. Power Management
14.1
Idle Mode
An instruction that sets PCON.0 indicates that it is the last instruction to be executed before
going into Idle mode. In Idle mode, the internal clock signal is gated off to the CPU, but not to the
interrupt, Timer, and Serial Port functions. The CPU status is preserved in its entirety: the Stack
Pointer, Program Counter, Program Status Word, Accumulator and all other registers maintain
their data during idle. The port pins hold the logical states they had at the time Idle was activated. ALE and PSEN hold at logic high level.
There are two ways to terminate the Idle mode. Activation of any enabled interrupt will cause
PCON.0 to be cleared by hardware, terminating the Idle mode. The interrupt will be serviced,
and following RETI the next instruction to be executed will be the one following the instruction
that put the device into idle.
The flag bits GF0 and GF1 can be used to give an indication if an interrupt occurred during normal operation or during idle. For example, an instruction that activates idle can also set one or
both flag bits. When idle is terminated by an interrupt, the interrupt service routine can examine
the flag bits.
The other way of terminating the Idle mode is with a hardware reset. Since the clock oscillator is
still running, the hardware reset needs to be held active for only two machine cycles (24 oscillator periods) to complete the reset.
14.2
Power-down Mode
To save maximum power, a power-down mode can be invoked by software (refer to Table 1112, PCON register).
In power-down mode, the oscillator is stopped and the instruction that invoked power-down
mode is the last instruction executed. The internal RAM and SFRs retain their value until the
power-down mode is terminated. VCC can be lowered to save further power. Either a hardware
reset or an external interrupt can cause an exit from power-down. To properly terminate powerdown, the reset or external interrupt should not be executed before VCC is restored to its normal
operating level and must be held active long enough for the oscillator to restart and stabilize.
Only external interrupts INT0, INT1 and Keyboard Interrupts are useful to exit from power-down.
Thus, the interrupt must be enabled and configured as level - or edge - sensitive interrupt input.
When Keyboard Interrupt occurs after a power-down mode, 1024 clocks are necessary to exit to
power-down mode and enter in operating mode.
Holding the pin low restarts the oscillator but bringing the pin high completes the exit as detailed
in Figure 14-1. When both interrupts are enabled, the oscillator restarts as soon as one of the
two inputs is held low and power-down exit will be completed when the first input is released. In
this case, the higher priority interrupt service routine is executed. Once the interrupt is serviced,
the next instruction to be executed after RETI will be the one following the instruction that put
AT83C51RB2/RC2 into power-down mode.
56
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Figure 14-1. Power-down Exit Waveform
INT0
INT1
XTAL
Active Phase
Power-down Phase
OscillatoR Restart
Active Phase
Exit from power-down by reset redefines all the SFRs, exit from power-down by external interrupt does no affect the SFRs.
Exit from power-down by either reset or external interrupt does not affect the internal RAM
content.
Note:
If idle mode is activated with power-down mode (IDL and PD bits set), the exit sequence is
unchanged, when execution is vectored to interrupt, PD and IDL bits are cleared and idle mode is
not entered.
Table 14-1 shows the state of ports during idle and power-down modes.
Table 14-1.
State of Ports
Mode
Program Memory
ALE
PSEN
PORT0
PORT1
PORT2
PORT3
Idle
Internal
1
1
Port Data(1)
Port Data
Port Data
Port Data
Idle
External
1
1
Floating
Port Data
Address
Port Data
Power-down
Internal
0
0
Port Dat(1)
Port Data
Port Data
Port Data
Power-down
External
0
0
Floating
Port Data
Port Data
Port Data
Note:
1. Port 0 can force a 0 level. A "one" will leave port floating.
57
4114B–8051–01/09
15. Hardware Watchdog Timer
The WDT is intended as a recovery method in situations where the CPU may be subjected to
software upset. The WDT consists of a 14-bit counter and the WatchDog Timer Reset
(WDTRST) SFR. The WDT is by default disabled from exiting reset. To enable the WDT, user
must write 01EH and 0E1H in sequence to the WDTRST, SFR location 0A6H. When WDT is
enabled, it will increment every machine cycle while the oscillator is running and there is no way
to disable the WDT except through reset (either hardware reset or WDT overflow reset). When
WDT overflows, it will drive an output RESET HIGH pulse at the RST-pin.
15.1
Using the WDT
To enable the WDT, user must write 01EH and 0E1H in sequence to the WDTRST, SFR location 0A6H. When WDT is enabled, the user needs to service it by writing to 01EH and 0E1H to
WDTRST to avoid WDT overflow. The 14-bit counter overflows when it reaches 16383 (3FFFH)
and this will reset the device. When WDT is enabled, it will increment every machine cycle while
the oscillator is running. Therefore, the user must reset the WDT at least every 16383 machine
cycles. To reset the WDT the user must write 01EH and 0E1H to WDTRST. WDTRST is a write
only register. The WDT counter cannot be read or written. When WDT overflows, it will generate
an output RESET pulse at the RST-pin. The RESET pulse duration is 96 x TCLK PERIPH, where
TCLK PERIPH= 1/FCLK PERIPH. To make the best use of the WDT, it should be serviced in those sections of code that will periodically be executed within the time required to prevent a WDT reset.
To have a more powerful WDT, a 27 counter has been added to extend the Time-out capability,
ranking from 16 ms to 2s @ Fosc = 12 MHz. To manage this feature, refer to WDTPRG register
description, Table 15-1.
Table 15-1. WDTRST Register
WDTRST - Watchdog Reset Register (0A6h)
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
-
Reset Value = XXXX XXXXb
Write only, this SFR is used to reset/enable the WDT by writing 01EH then 0E1H in sequence.
58
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 15-2. WDTPRG Register
WDTPRG - Watchdog Timer Out Register (0A7h)
7
6
5
4
3
2
1
0
-
-
-
-
-
S2
S1
S0
Bit
Number
Bit
Mnemonic Description
7
-
6
-
5
-
4
-
3
-
2
S2
WDT Time-out select bit 2
1
S1
WDT Time-out select bit 1
0
S0
WDT Time-out select bit 0
Reserved
The value read from this bit is undetermined. Do not try to set this bit.
S2S1 S0Selected Time-out
0 0
0
(214 - 1) machine cycles, 16. 3 ms @ Fosc =12 MHz
0 0
1
(215 - 1) machine cycles, 32.7 ms @ Fosc=12 MHz
0 1
0 (216 - 1) machine cycles, 65. 5 ms @ Fosc=12 MHz
0 1
1
(217 - 1) machine cycles, 131 ms @ Fosc=12 MHz
1 0
0
(218 - 1) machine cycles, 262 ms @ Fosc=12 MHz
1 0
1 (219 - 1) machine cycles, 542 ms @ Fosc=12 MHz
1 1
0
(220 - 1) machine cycles, 1.05 s @ Fosc=12 MHz
1 1
1
(221 - 1) machine cycles, 2.09 s @ Fosc=12 MHz
Reset Value = XXXX X000
15.2
WDT During Power-down and Idle
In Power-down mode the oscillator stops, which means the WDT also stops. While in Powerdown mode the user does not need to service the WDT. There are 2 methods of exiting Powerdown mode: by a hardware reset or via a level activated external interrupt which is enabled prior
to entering Power-down mode. When Power-down is exited with hardware reset, servicing the
WDT should occur as normal, whenever the AT83C51RB2/RC2 is reset. Exiting Power-down
with an interrupt is significantly different. The interrupt is held low long enough for the oscillator
to stabilize. When the interrupt is brought high, the interrupt is serviced. To prevent the WDT
from resetting the device while the interrupt pin is held low, the WDT is not started until the interrupt is pulled high. It is suggested that the WDT be reset during the interrupt service routine.
To ensure that the WDT does not overflow within a few states of exiting of power-down, it is better to reset the WDT just before entering power-down.
In the Idle mode, the oscillator continues to run. To prevent the WDT from resetting the
AT83C51RB2/RC2 while in Idle mode, the user should always set up a timer that will periodically
exit Idle, service the WDT, and re-enter Idle mode.
59
4114B–8051–01/09
16. Power-off Flag
The Power-off flag allows the user to distinguish between a “cold start” reset and a “warm start”
reset.
A cold start reset is the one induced by VCC switch-on. A warm start reset occurs while VCC is still
applied to the device and could be generated for example by an exit from power-down.
The Power-off flag (POF) is located in PCON register (Table 16-1). POF is set by hardware
when VCC rises from 0 to its nominal voltage. The POF can be set or cleared by software allowing the user to determine the type of reset.
Table 16-1. PCON Register
PCON - Power Control Register (87h)
7
6
5
4
3
2
1
0
SMOD1
SMOD0
-
POF
GF1
GF0
PD
IDL
Bit
Number
Bit
Mnemonic Description
7
SMOD1
Serial port Mode bit 1
Set to select double baud rate in mode 1, 2 or 3.
6
SMOD0
Serial port Mode bit 0
Cleared to select SM0 bit in SCON register.
Set to select FE bit in SCON register.
5
-
Reserved
The value read from this bit is indeterminate. Do not set this bit.
4
POF
Power-off Flag
Cleared to recognize next reset type.
Set by hardware when VCC rises from 0 to its nominal voltage. Can also be set by
software.
3
GF1
General purpose Flag
Cleared by user for general purpose usage.
Set by user for general purpose usage.
2
GF0
General purpose Flag
Cleared by user for general purpose usage.
Set by user for general purpose usage.
1
PD
Power-down mode bit
Cleared by hardware when reset occurs.
Set to enter power-down mode.
0
IDL
Idle mode bit
Cleared by hardware when interrupt or reset occurs.
Set to enter idle mode.
Reset Value = 00X1 0000b
Not bit addressable
60
AT83C51RB2/RC2
4114B–8051–01/09
16. ROM
16.1
ROM Structure
The T89C51RB2/RC2 ROM memory is divided in two different arrays:
• The code array:16/32K bytes.
• The config byte: 1 byte.
16.1.1
Hardware Config Byte
The config byte sets the starting microcontroller options and the security levels.
The starting options are X2 mode, and XRAM.
7
6
5
4
3
2
1
0
X2
-
-
-
XRAM
-
LB1
LB0
Bit
Bit
Number
Mnemonic
7
X2
Description
X2 Mode
Cleared to force X2 mode (6 clocks per instruction)
Set to force X1 mode, Standard Mode.
6
-
Reserved
5
-
Reserved
4
-
Reserved
3
XRAM
XRAM config bit
Set this bit to enable XRAM.
Clear this bit to disable XRAM.
16.2
2
-
1-0
LB0-1
Reserved
User Program ROM Lock Bits
see Table 16-1.
ROM Lock System
The program Lock system, when programmed, protects the on-chip program against software
piracy.
60
AT83C51RB2/RC2
4114B–8051–01/08
AT83C51RB2/RC2
16.2.1
Program ROM Lock Bits
Table 16-1.
Program Lock bits
Program Lock Bits
Notes:
Protection Description
Security
level
LB0
LB1
1
U
U
No program lock features enabled.
2
P
U
Reserved. Do not use.
3
U
P
MOVC instruction executed from external program memory are disabled from
fetching code bytes from internal memory, EA is sampled and latched on reset.
Verify disable.
1. U: unprogrammed
P: programmed
2. The lock bits when programmed according to Table 16-1 will provide different level of protection for the on-chip code and data.
61
4114B–8051–01/08
AT83C51RB2/RC2
17. Reduced EMI Mode
The ALE signal is used to demultiplex address and data buses on port 0 when used with external program or data memory. Nevertheless, during internal code execution, ALE signal is still
generated. In order to reduce EMI, ALE signal can be disabled by setting AO bit.
The AO bit is located in AUXR register at bit location 0. As soon as AO is set, ALE is no longer
output but remains active during MOVX and MOVC instructions and external fetches. During
ALE disabling, ALE pin is weakly pulled high.
Table 17-1. AUXR Register
AUXR - Auxiliary Register (8Eh)
7
6
5
4
3
2
1
0
-
-
M0
-
XRS1
XRS0
EXTRAM
AO
Bit
Number
Bit
Mnemonic Description
7
-
6
-
Reserved
The value read from this bit is indeterminate. Do not set this bit
Reserved
The value read from this bit is indeterminate. Do not set this bit
Pulse length
5
M0
Cleared to stretch MOVX control: the RD and the WR pulse length is 6 clock
periods (default).
Set to stretch MOVX control: the RD and the WR pulse length is 30 clock
periods.
4
-
3
XRS1
Reserved
The value read from this bit is indeterminate. Do not set this bit
XRAM Size
XRS1XRS0XRAM Size
0 0256 bytes (default)
2
XRS0
0
1512 bytes
1
0768 bytes
1
11024 bytes
EXTRAM bit
Cleared to access internal XRAM using movx @ Ri/ @ DPTR.
1
EXTRAM
Set to access external memory.
Programmed by hardware after Power-up regarding Hardware Security Byte
(HSB), default setting, XRAM selected.
0
AO
ALE Output bit
Cleared, ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if
X2 mode is used) (default). Set, ALE is active only during a MOVX or MOVC
instructione is used.
61
4114B–8051–01/09
62
AT83C51RB2/RC2
4114B–8051–01/09
17. Electrical Characteristics
Table 17-1.
Absolute Maximum Ratings
Note:
Stresses at or above those listed under “Absolute
Maximum Ratings” may cause permanent damage to
the device. This is a stress rating only and functional
operation of the device at these or any other conditions above those indicated in the operational sections
of this specification is not implied. Exposure to absolute maximum rating conditions may affect device
reliability.
Power dissipation value is based on the maximum
allowable die temperature and the thermal resistance
of the package.
C = commercial......................................................0°C to 70°C
I = industrial ........................................................-40°C to 85°C
Storage Temperature .................................... -65°C to + 150°C
Voltage on VCC to VSS (standard voltage) .........-0.5V to + 6.5V
Voltage on VCC to VSS (low voltage)..................-0.5V to + 4.5V
Voltage on Any Pin to VSS ..........................-0.5V to VCC + 0.5V
Power Dissipation .............................................................. 1 W
17.1
DC Parameters for Standard Voltage
TA = 0°C to +70°C; VSS = 0V; VCC = 4.5V to 5.5V; F = 10 to 40 MHz
TA = -40°C to +85°C; VSS = 0V; VCC =4.5V to 5.5V; F = 10 to 40 MHz
Symbol
Parameter
Min
VIL
Input Low Voltage
VIH
Input High Voltage except RST, XTAL1
VIH1
Input High Voltage RST, XTAL1
VOL
VOL1
VOH
VOH1
RRST
60
Output Low Voltage, ports 1, 2, 3, 4
Typ
Max
Unit
-0.5
0.2 VCC - 0.1
V
0.2 VCC + 0.9
VCC + 0.5
V
0.7 VCC
VCC + 0.5
V
0.3
V
IOL = 100 μA(4)
0.45
V
IOL = 1.6 mA(4)
1.0
V
IOL = 3.5 mA(4)
(6)
Output Low Voltage, port 0, ALE, PSEN (6)
Output High Voltage, ports 1, 2, 3, 4
Output High Voltage, port 0, ALE, PSEN
RST Pull-down Resistor
0.3
V
IOL = 200 μA(4)
0.45
V
IOL = 3.2 mA(4)
1.0
V
IOL = 7.0 mA(4)
VCC - 0.3
V
VCC - 0.7
V
VCC - 1.5
V
VCC - 0.3
V
VCC - 0.7
V
VCC - 1.5
V
50
(5)
200
Test Conditions
250
kΩ
IOH = -10 μA
IOH = -30 μA
IOH = -60 μA
VCC = 5V ± 10%
IOH = -200 μA
IOH = -3.2 mA
IOH = -7.0 mA
VCC = 5V ± 10%
IIL
Logical 0 Input Current ports 1, 2, 3, 4 and 5
-50
μA
VIN = 0.45V
ILI
Input Leakage Current
±10
μA
0.45V < VIN < VCC
ITL
Logical 1 to 0 Transition Current, ports 1, 2, 3, 4
-650
μA
VIN = 2.0 V
CIO
Capacitance of I/O Buffer
10
pF
Fc = 3 MHz
TA = 25°C
IPD
Power-down Current
150
μA
4.5V < VCC < 5.5V(3)
100
ICCOP
Power Supply Current on normal mode
0.29 x Frequency (MHz) + 4
mA
VCC = 5.5V(1)
ICCIDLE
Power Supply Current on idle mode
0.16 x Frequency (MHz) + 4
mA
VCC = 5.5V(2)
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
17.2
DC Parameters for Standard Voltage (2)
TA = 0°C to +70°C; VSS = 0 V; VCC = 2.7V to 5.5V; F = 10 to 40 MHz
TA = -40°C to +85°C; VSS = 0 V; VCC = 2.7V to 5.5V; F = 10 to 40 MHz
Symbol
Parameter
Min
VIL
Input Low Voltage
VIH
Input High Voltage except XTAL1, RST
VIH1
Input High Voltage, XTAL1, RST
VOL
Typ(5)
Max
Unit
Test Conditions
-0.5
0.2 VCC - 0.1
V
0.2 VCC + 0.9
VCC + 0.5
V
0.7 VCC
VCC + 0.5
V
Output Low Voltage, ports 1, 2, 3, 4 and 5 (6)
0.45
V
IOL = 0.8 mA(4)
VOL1
Output Low Voltage, port 0, ALE, PSEN (6)
0.45
V
IOL = 1.6 mA(4)
VOH
Output High Voltage, ports 1, 2, 3, 4 and 5
0.9 VCC
V
IOH = -10 μA
VOH1
Output High Voltage, port 0, ALE, PSEN
0.9 VCC
V
IOH = -40 μA
IIL
Logical 0 Input Current ports 1, 2, 3, 4 and 5
-50
μA
VIN = 0.45V
ILI
Input Leakage Current
±10
μA
0.45V < VIN < VCC
ITL
Logical 1 to 0 Transition Current, ports 1, 2, 3, 4
and 5
-650
μA
VIN = 2.0V
250
kΩ
10
pF
Fc = 3 MHz
TA = 25°C
150
μA
VCC =2.7V to 5.5V(3)
RRST
RST Pulldown Resistor
CIO
Capacitance of I/O Buffer
IPD
Power-down Current
50
200
120
ICCOP
Power Supply Current on normal mode
0.29 x Frequency (MHz) + 4
mA
VCC = 5.5V(1)
ICCIDLE
Power Supply Current on idle mode
0.16 x Frequency (MHz) + 4
mA
VCC = 5.5V(2)
Notes:
1. Operating ICC is measured with all output pins disconnected; XTAL1 driven with TCLCH, TCHCL = 5 ns (see Figure 17-4.),
VIL = VSS + 0.5V,
VIH = VCC - 0.5V; XTAL2 N.C.; EA = RST = Port 0 = VCC. ICC would be slightly higher if a crystal oscillator used (see Figure
17-1).
2. Idle ICC is measured with all output pins disconnected; XTAL1 driven with TCLCH, TCHCL = 5 ns, VIL = VSS + 0.5V,
VIH = VCC - 0.5V; XTAL2 N.C; Port 0 = VCC; EA = RST = VSS (see Figure 17-2).
3. Power-down ICC is measured with all output pins disconnected; EA = VSS, PORT 0 = VCC; XTAL2 NC.; RST = VSS (see Figure
17-3).
4. Capacitance loading on Ports 0 and 2 may cause spurious noise pulses to be superimposed on the VOLs of ALE and Ports 1
and 3. The noise is due to external bus capacitance discharging into the Port 0 and Port 2 pins when these pins make 1 to 0
transitions during bus operation. In the worst cases (capacitive loading 100pF), the noise pulse on the ALE line may exceed
0.45V with maxi VOL peak 0.6V. A Schmitt Trigger use is not necessary.
5. Typical are based on a limited number of samples and are not guaranteed. The values listed are at room temperature and
5V.
6. Under steady state (non-transient) conditions, IOL must be externally limited as follows:
Maximum IOL per port pin: 10 mA
Maximum IOL per 8-bit port:
Port 0: 26 mA
Ports 1, 2 and 3: 15 mA
Maximum total IOL for all output pins: 71 mA
If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater
than the listed test conditions.
7. For other values, please contact your sales office.
61
4114B–8051–01/09
Figure 17-1. ICC Test Condition, Active Mode
VCC
ICC
VCC
VCC
P0
VCC
RST
EA
XTAL2
XTAL1
(NC)
CLOCK
SIGNAL
VSS
All other pins are disconnected.
Figure 17-2. ICC Test Condition, Idle Mode
VCC
ICC
VCC
VCC
P0
RST
EA
XTAL2
XTAL1
VSS
(NC)
CLOCK
SIGNAL
All other pins are disconnected.
Figure 17-3. ICC Test Condition, Power-down Mode
VCC
ICC
VCC
VCC
P0
RST
(NC)
EA
XTAL2
XTAL1
VSS
All other pins are disconnected.
62
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Figure 17-4. Clock Signal Waveform for ICC Tests in Active and Idle Modes
VCC-0.5V
0.45V
TCLCH
TCHCL
TCLCH = TCHCL = 5ns.
17.3
17.3.1
0.7VCC
0.2VCC-0.1
AC Parameters
Explanation of the AC Symbols
Each timing symbol has 5 characters. The first character is always a “t” (stands for time). The
other characters, depending on their positions, stand for the name of a signal or the logical status of that signal. The following is a list of all the characters and what they stand for.
Example:TAVLL = Time for Address Valid to ALE Low.
TLLPL = Time for ALE Low to PSEN Low.
(Load Capacitance for port 0, ALE and PSEN = 100 pF; Load Capacitance for all other outputs =
80 pF.)
Table 17-2 Table 17-5, and Table 17-7 give the description of each AC symbols.
Table 17-4, Table 17-6 and Table 17-8 give for each range the AC parameter.
Table 17-3, Table 17-4 and Table 17-9 gives the frequency derating formula of the AC parameter for each speed range description. To calculate each AC symbols. take the x value in the
correponding column and use this value in the formula.
Example: TLLIU for 20 MHz, Standard clock.
x = 35 ns
T = 50 ns
TCCIV = 4T - x = 165 ns
63
4114B–8051–01/09
17.3.2
External Program Memory Characteristics
Table 17-2. Symbol Description
Symbol
T
Table 17-3.
Parameter
Oscillator clock period
TLHLL
ALE pulse width
TAVLL
Address Valid to ALE
TLLAX
Address Hold After ALE
TLLIV
ALE to Valid Instruction In
TLLPL
ALE to PSEN
TPLPH
PSEN Pulse Width
TPLIV
PSEN to Valid Instruction In
TPXIX
Input Instruction Hold After PSEN
TPXIZ
Input Instruction FloatAfter PSEN
TAVIV
Address to Valid Instruction In
TPLAZ
PSEN Low to Address Float
AC Parameters for a Fix Clock
Symbol
-M
Min
Max
T
25
ns
TLHLL
35
ns
TAVLL
5
ns
TLLAX
5
ns
TLLIV
65
ns
TLLPL
5
ns
TPLPH
50
ns
TPLIV
TPXIX
64
Units
30
0
ns
ns
TPXIZ
10
ns
TAVIV
80
ns
TPLAZ
10
ns
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 17-4.
17.3.3
AC Parameters for a Variable Clock
Symbol
Type
Standard
Clock
X2 Clock
X Parameter for M Range
Units
TLHLL
Min
2T-x
T-x
15
ns
TAVLL
Min
T-x
0.5 T - x
20
ns
TLLAX
Min
T-x
0.5 T - x
20
ns
TLLIV
Max
4T-x
2T-x
35
ns
TLLPL
Min
T-x
0.5 T - x
15
ns
TPLPH
Min
3T-x
1.5 T - x
25
ns
TPLIV
Max
3T-x
1.5 T - x
45
ns
TPXIX
Min
x
x
0
ns
TPXIZ
Max
T-x
0.5 T - x
15
ns
TAVIV
Max
5T-x
2.5 T - x
45
ns
TPLAZ
Max
x
x
10
ns
External Program Memory Read Cycle
12 TCLCL
TLHLL
TLLIV
ALE
TLLPL
TPLPH
PSEN
TLLAX
TAVLL
PORT 0
INSTR IN
TPLIV
TPLAZ
A0-A7
TPXAV
TPXIZ
TPXIX
INSTR IN
A0-A7
INSTR IN
TAVIV
PORT 2
17.3.4
ADDRESS
OR SFR-P2
ADDRESS A8 - A15
ADDRESS A8-A15
External Data Memory Characteristics
65
4114B–8051–01/09
Table 17-5.
Symbol Description
Symbol
Table 17-6.
Parameter
TRLRH
RD Pulse Width
TWLWH
WR Pulse Width
TRLDV
RD to Valid Data In
TRHDX
Data Hold After RD
TRHDZ
Data Float After RD
TLLDV
ALE to Valid Data In
TAVDV
Address to Valid Data In
TLLWL
ALE to WR or RD
TAVWL
Address to WR or RD
TQVWX
Data Valid to WR Transition
TQVWH
Data set-up to WR High
TWHQX
Data Hold After WR
TRLAZ
RD Low to Address Float
TWHLH
RD or WR High to ALE high
AC Parameters for a Fix Clock
-M
Symbol
Min
TRLRH
125
ns
TWLWH
125
ns
TRLDV
TRHDX
66
Max
95
Units
ns
0
ns
TRHDZ
25
ns
TLLDV
155
ns
TAVDV
160
ns
105
ns
TLLWL
45
TAVWL
70
ns
TQVWX
5
ns
TQVWH
155
ns
TWHQX
10
ns
TRLAZ
0
ns
TWHLH
5
45
ns
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
17.3.5
Symbol
Type
Standard
Clock
X2 Clock
X parameter for M range
Units
TRLRH
Min
6T-x
3T-x
25
ns
TWLWH
Min
6T-x
3T-x
25
ns
TRLDV
Max
5T-x
2.5 T - x
30
ns
TRHDX
Min
x
x
0
ns
TRHDZ
Max
2T-x
T-x
25
ns
TLLDV
Max
8T-x
4T -x
45
ns
TAVDV
Max
9T-x
4.5 T - x
65
ns
TLLWL
Min
3T-x
1.5 T - x
30
ns
TLLWL
Max
3T+x
1.5 T + x
30
ns
TAVWL
Min
4T-x
2T-x
30
ns
TQVWX
Min
T-x
0.5 T - x
20
ns
TQVWH
Min
7T-x
3.5 T - x
20
ns
TWHQX
Min
T-x
0.5 T - x
15
ns
TRLAZ
Max
x
x
0
ns
TWHLH
Min
T-x
0.5 T - x
20
ns
TWHLH
Max
T+x
0.5 T + x
20
ns
External Data Memory Write Cycle
TWHLH
ALE
PSEN
TLLWL
TWLWH
WR
TLLAX
PORT 0
A0-A7
TQVWX
TQVWH
TWHQX
DATA OUT
TAVWL
PORT 2
ADDRESS
OR SFR-P2
ADDRESS A8 - A15 OR SFR P2
67
4114B–8051–01/09
17.3.6
External Data Memory Read Cycle
TWHLH
TLLDV
ALE
PSEN
TLLWL
TRLRH
RD
TRHDZ
TAVDV
TLLAX
PORT 0
TRHDX
A0-A7
DATA IN
TRLAZ
TAVWL
PORT 2
17.3.7
ADDRESS
OR SFR-P2
ADDRESS A8-A15 OR SFR P2
Serial Port Timing - Shift Register Mode
Table 17-7. Symbol Description
Symbol
Table 17-8.
Parameter
TXLXL
Serial port clock cycle time
TQVHX
Output data set-up to clock rising edge
TXHQX
Output data hold after clock rising edge
TXHDX
Input data hold after clock rising edge
TXHDV
Clock rising edge to input data valid
AC Parameters for a Fix Clock
-M
Symbol
Min
TXLXL
300
ns
TQVHX
200
ns
TXHQX
30
ns
TXHDX
0
ns
TXHDV
68
Max
117
Units
ns
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Table 17-9.
17.3.8
AC Parameters for a Variable Clock
Symbol
Type
Standard
Clock
X2 Clock
X Parameter for M Range
TXLXL
Min
12 T
6T
TQVHX
Min
10 T - x
5T-x
50
ns
TXHQX
Min
2T-x
T-x
20
ns
TXHDX
Min
x
x
0
ns
TXHDV
Max
10 T - x
5 T- x
133
ns
Units
ns
Shift Register Timing Waveforms
INSTRUCTION
0
1
2
3
4
5
6
7
8
ALE
TXLXL
CLOCK
TXHQX
TQVXH
0
OUTPUT DATA
WRITE to SBUF
1
2
4
5
6
7
TXHDX
TXHDV
INPUT DATA
3
VALID
VALID
VALID
SET TI
VALID
VALID
VALID
VALID
SET RI
CLEAR RI
17.3.9
VALID
External Clock Drive Waveforms
VCC-0.5V
0.45V
0.7VCC
0.2VCC-0.1
TCHCL
TCHCX
TCLCH
TCLCX
TCLCL
17.3.10
AC Testing Input/Output Waveforms
VCC -0.5V
INPUT/OUTPUT
0.45V
0.2 VCC + 0.9
0.2 VCC - 0.1
AC inputs during testing are driven at VCC - 0.5 for a logic “1” and 0.45V for a logic “0”. Timing
measurement are made at VIH min for a logic “1” and VIL max for a logic “0”.
69
4114B–8051–01/09
17.3.11
Float Waveforms
FLOAT
VOH - 0.1 V
VOL + 0.1 V
VLOAD
VLOAD + 0.1 V
VLOAD - 0.1 V
For timing purposes as port pin is no longer floating when a 100 mV changes from load voltage
occurs and begins to float when a 100 mV change from the loaded VOH/VOL level occurs. IOL/IOH
≥ ± 20 mA.
17.3.12
70
Clock Waveforms
Valid in normal clock mode. In X2 mode XTAL2 must be changed to XTAL2/2.
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
Figure 17-5. Internal Clock Signals
INTERNAL
CLOCK
STATE4
STATE5
STATE6
STATE1
STATE2
STATE3
STATE4
STATE5
P1
P1
P1
P1
P1
P1
P1
P1
P2
P2
P2
P2
P2
P2
P2
P2
XTAL2
ALE
THESE SIGNALS ARE NOT ACTIVATED DURING THE
EXECUTION OF A MOVX INSTRUCTION
EXTERNAL PROGRAM MEMORY FETCH
PSEN
P0
DATA
SAMPLED
FLOAT
P2 (EXT)
PCL OUT
DATA
SAMPLED
FLOAT
PCL OUT
DATA
SAMPLED
FLOAT
PCL OUT
INDICATES ADDRESS TRANSITIONS
READ CYCLE
RD
PCL OUT (IF PROGRAM
MEMORY IS EXTERNAL)
P0
DPL OR Rt OUT
P2
DATA
SAMPLED
FLOAT
INDICATES DPH OR P2 SFR TO PCH TRANSITION
WRITE CYCLE
WR
P0
PCL OUT (EVEN IF PROGRAM
MEMORY IS INTERNAL)
DPL OR Rt OUT
PCL OUT (IF PROGRAM
MEMORY IS EXTERNAL)
DATA OUT
P2
INDICATES DPH OR P2 SFR TO PCH TRANSITION
PORT OPERATION
MOV PORT SRC
OLD DATA NEW DATA
P0 PINS SAMPLED
P0 PINS SAMPLED
MOV DEST P0
MOV DEST PORT (P1. P2. P3)
(INCLUDES INTO. INT1. TO T1)
SERIAL PORT SHIFT CLOCK
P1, P2, P3 PINS SAMPLED
RXD SAMPLED
P1, P2, P3 PINS SAMPLED
RXD SAMPLED
TXD (MODE 0)
This diagram indicates when signals are clocked internally. The time it takes the signals to propagate to the pins, however,
ranges from 25 to 125 ns. This propagation delay is dependent on variables such as temperature and pin loading. Propagation also varies from output to output and component. Typically though (TA = 25°C fully loaded) RD and WR propagation
delays are approximately 50 ns. The other signals are typically 85 ns. Propagation delays are incorporated in the AC
specifications.
71
4114B–8051–01/09
AT83C51RB2/RC2
18. Ordering Information
Table 18-1.
Ordering Information
Part Number
Package
Temperature Range
Packing
AT83C51RB2xxx-3CSUM
PDIL40
Industrial & Green
Stick
AT83C51RB2xxx-SLSUM
PLCC44
Industrial & Green
Stick
AT83C51RB2xxx-RLTUM
VQFP44
Industrial & Green
Tray
AT83C51RB2xxx-SLRUM
PLCC44
Industrial & Green
Tape & Reel
AT83C51RB2xxx-RLRUM
VQFP44
Industrial & Green
Tape & Reel
AT83C51RC2xxx-3CSUM
PDIL40
Industrial & Green
Stick
AT83C51RC2xxx-SLSUM
PLCC44
Industrial & Green
Stick
AT83C51RC2xxx-RLTUM
VQFP44
Industrial & Green
Tray
AT83C51RC2xxx-SLRUM
PLCC44
Industrial & Green
Tape & Reel
AT83C51RC2xxx-RLRUM
VQFP44
Industrial & Green
Tape & Reel
63
4114B–8051–01/09
19. Package Information
19.1
64
PDIL40
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
19.2
PLCC44
65
4114B–8051–01/09
STANDARD NOTES FOR PLCC
1/ CONTROLLING DIMENSIONS : INCHES
2/ DIMENSIONING AND TOLERANCING PER ANSI Y 14.5M - 1982.
SIDE.
66
3/ "D" AND "E1" DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTUSIONS.
MOLD FLASH OR PROTUSIONS SHALL NOT EXCEED 0.20 mm (.008 INCH) PER
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
19.3
VQFP44
67
4114B–8051–01/09
STANDARD NOTES FOR PQFP/ VQFP / TQFP / DQFP
1/ CONTROLLING DIMENSIONS : INCHES
2/ ALL DIMENSIONING AND TOLERANCING CONFORM TO ANSI Y 14.5M 1982.
3/ "D1 AND E1" DIMENSIONS DO NOT INCLUDE MOLD PROTUSIONS.
MOLD PROTUSIONS SHALL NOT EXCEED 0.25 mm (0.010 INCH).
THE TOP PACKAGE BODY SIZE MAY BE SMALLER THAN THE BOTTOM
PACKAGE BODY SIZE BY AS MUCH AS 0.15 mm.
4/ DATUM PLANE "H" LOCATED AT MOLD PARTING LINE AND
COINCIDENT WITH LEAD, WHERE LEAD EXITS PLASTIC BODY AT
BOTTOM OF PARTING LINE.
5/ DATUM "A" AND "D" TO BE DETERMINED AT DATUM PLANE H.
6/ DIMENSION " f " DOES NOT INCLUDE DAMBAR PROTUSION ALLOWABLE
DAMBAR PROTUSION SHALL BE 0.08mm/.003" TOTAL IN EXCESS OF THE
" f " DIMENSION AT MAXIMUM MATERIAL CONDITION .
DAMBAR CANNOT BE LOCATED ON THE LOWER RADIUS OR THE FOOT.
68
AT83C51RB2/RC2
4114B–8051–01/09
AT83C51RB2/RC2
20. Datasheet Change Log
20.1
Changes from 4113A - 09/02 to 4113B -03/05
1. Added Green product ordering information.
20.2
Changes from 4113B -03/05 to 4113C -01/08
1. Removed AT80C51RD2 product offering Table 18-1 on page 63.
2. Updated Package Drawings.
20.3
Changes from 4113C -01/08 to 4113D -01/09
1. Removed AT83C51RD2 product offering
69
4114B–8051–01/09