ETC VRS51C540-40-LG

VRS51x540
Datasheet
Rev 1.2
Versa 8051 MCU with 4KB Flash
Overview
Feature Set
The VRS51x540 is a low cost 8-bit microcontroller
based on the standard 80C51 microcontroller family
architecture. It is pin compatible and is a drop-in
replacement for standard 8051 MCUs
Aimed at cost effective applications requiring small
amounts of program/data memory coupled with
streamlined peripheral support, the VRS51x540 includes
4KB of Flash memory, 128 bytes of RAM a UART, three
16-bit timers, a Watchdog timer and power down
features.
The VRS51x540 is available in 5 (VRS51C540) and 3.3
(VRS51L540) volt versions in PLCC-44, QFP-44 and
DIP-40 packages. The VRS51x540 devices operate
over the entire industrial temperature range. The Flash
memory can be programmed using programmers
available from Ramtron or other 3rd party commercial
programmers.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
80C51/80C52 pin compatible
12 clock periods per machine cycle
4KB on-chip Flash memory
128 bytes on-chip data RAM
32 I/O lines: P0-P3 = 8-bit
Full duplex serial port (UART)
3, 16-bit Timers/Counters
Watchdog Timer
8-bit Unsigned Division / Multiply
BCD arithmetic
Direct and Indirect Addressing
Two levels of interrupt priority and nested interrupts
Power saving modes
Code protection function
Operates at a clock frequency of up to 40MHz
Low EMI (inhibit ALE)
Programming voltage: 12V
Industrial Temperature range (-40°C to +85°C)
5V and 3V versions available (see ordering information.)
FIGURE 2: VRS51X540 PLCC AND QFP PINOUT DIAGRAMS
8051
PROCESSOR
P1.5
ADDRESS/
DATA BUS
7
6
PORT 0
P0.3/AD3
P0.2/AD2
P0.1/AD1
P0.0/AD0
NC
VDD
40
1
P0.4/AD4
39
P1.6
P0.5/AD5
P0.6/AD6
P1.7
RESET
RXD/P3.0
4KB
FLASH
T2/P1.0
P1.2
T2EX/P1.1
P1.3
P1.4
FIGURE 1: VRS51X540 FUNCTIONAL DIAGRAM
8
P0.7/AD7
#EA
VRS51x540
PLCC-44
NC
TXD/P3.1
NC
ALE
#PSEN
P2.7/A15
#INT0/P3.2
#INT1/P3.3
TIMER 0
P2.6/A14
P2.5/A13
P2.4/A12
P2.3/A11
P2.2/A10
#PSEN
P2.7/A15
P2.1/A9
P2.0/A8
3
3 3
4
2
32
2
P0.0/AD0
VDD
WATCHDOG
TIMER
P2.1/A9
P2.0/A8
VRS51x540
QFP-44
NC
T2/P1.0
NC
VSS
T2EX/P1.1
P1.2
XTAL1
XTAL2
Ramtron International Corporation
1850 Ramtron Drive Colorado Springs
Colorado, USA, 80921
?
?
?
#INT1/P3.3
TXD/P3.1
#INT0/P3.2
#RD/P3.7
#WR/P3.6
T0/P3.4
T1/P3.5
1
12
1
1
NC
4
4
RESET
RXD/P3.0
P1.3
P1.4
P2.4/A12
P2.3/A11
P2.2/A10
P1.7
RESET
P2.6/A14
P2.5/A13
29
P0.2/AD2
P0.1/AD1
P1.6
TIMER 2
P0.3/AD3
POWER
CONTROL
P1.5
TIMER 1
NC
ALE
8
NC
PORT 3
P0.7/AD7
#EA
2 INTERRUPT
INPUTS
VSS
8
XTAL2
XTAL1
PORT 2
28
#RD/P3.7
UART
17
18
#WR/P3.6
8
P0.5/AD5
P0.6/AD6
PORT 1
P0.4/AD4
T0/P3.4
T1/P3.5
128 Bytes of
RAM
http://www.ramtron.com
MCU customer service: 1-800-943-4625, 1-514-871-2447, ext. 208
1-800-545-FRAM, 1-719-481-7000
page 1 of 40
VRS51x540
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Bit 5 of Port 1
Bit 6 of Port 1
Bit 7 of Port 1
Reset
Receive Data
Bit 0 of Port 3
No Connect
Transmit Data &
Bit 1 of Port 3
External Interrupt 0
Bit 2 of Port 3
External Interrupt 1
Bit 3 of Port 3
Timer 0
Bit 4 of Port 3
Timer 1 & 3
Bit 5 of Port
Ext. Memory Write
Bit 6 of Port 3
Ext. Memory Read
Bit 7 of Port 3
Oscillator/Crystal Output
Oscillator/Crystal In
Ground
No Connect
Bit 0 of Port 2
Bit 8 of External Memory Address
Bit 1 of Port 2
Bit 9 of External Memory Address
Bit 2 of Port 2
Bit 10 of External Memory Address
Bit 3 of Port 2 &
Bit 11 of External Memory Address
Bit 4 of Port 2
Bit 12 of External Memory Address
Bit 5 of Port 2
Bit 13 of External Memory Address
42
43
Bit 6 of Port 2
Bit 14 of External Memory Address
Bit 7 of Port 2
Bit 15 of External Memory Address
Program Store Enable
Address Latch Enable
No Connect
External Access
Bit 7 Of Port 0
Data/Address Bit 7 of External Memory
Bit 6 of Port 0
Data/Address Bit 6 of External Memory
Bit 5 of Port 0
Data/Address Bit 5 of External Memory
Bit 4 of Port 0
Data/Address Bit 4 of External Memory
Bit 3 Of Port 0
Data/Address Bit 3 of External Memory
Bit 2 of Port 0
Data/Address Bit 2 of External Memory
Bit 1 of Port 0 & Data
Address Bit 1 of External Memory
Bit 0 Of Port 0 & Data
Address Bit 0 of External Memory
VCC
No Connect
Timer 2 Clock Out
Bit 0 of Port 1
Timer 2 Control
Bit 1 of Port 1
Bit 2 of Port 1
Bit 3 of Port 1
44
P1.4
I/O
Bit 4 of Port 1
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
P0.3/AD3
3
3 3
4
P2.6/A14
P2.5/A13
8
I/O
I/O
I/O
I
I
I/O
O
I/O
I
I/O
I
I/O
I
I/O
I
I/O
O
I/O
O
I/O
O
I
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
O
O
I
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I
I/O
I
I/O
I/O
I/O
P2.7/A15
7
P1.5
P1.6
P1.7
RES
RXD
P3.0
NC
TXD
P3.1
#INT0
P3.2
#INT1
P3.3
T0
P3.4
T1
P3.5
#WR
P3.6
#RD
P3.7
XTAL2
XTAL1
VSS
NC
P2.0
A8
P2.1
A9
P2.2
A10
P2.3
A11
P2.4
A12
P2.5
A13
P2.6
A14
P2.7
A15
#PSEN
ALE
NC
#EA
P0.7
AD7
P0.6
AD6
P0.5
AD5
P0.4
AD4
P0.3
AD3
P0.2
AD2
P0. 1
AD1
P0.0
AD0
VDD
NC
T2
P1.0
T2EX
P1.1
P1.2
P1.3
24
#PSEN
6
Function
Function
NC
ALE
5
I/O
I/O
P0.7/AD7
#EA
1
2
3
4
Name
Name
P0.6/AD6
QFP
- 44
QFP
- 44
P0.5/AD5
T ABLE 1: PIN DESCRIPTIONS FOR QFP-44/
P0.4/AD4
Pin Descriptions for QFP-44
2
32
2
P0.2/AD2
P0.1/AD1
P0.0/AD0
VDD
P2.1/A9
P2.0/A8
VRS51x540
QFP-44
NC
T2/P1.0
NC
VSS
T2EX/P1.1
P1.2
XTAL1
XTAL2
#INT1/P3.3
#INT0/P3.2
NC
TXD/P3.1
RESET
RXD/P3.0
P1.7
#RD/P3.7
#WR/P3.6
T0/P3.4
T1/P3.5
1
12
1
1
P1.6
4
4
P1.5
P1.3
P1.4
P2.4/A12
P2.3/A11
P2.2/A10
________________________________________________________________________________________________
www.ramtron.com
page 2 of 40
VRS51x540
Pin Descriptions for PLCC-44
14
15
16
17
18
19
20
21
22
23
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
I/O
P0.6
I/O
AD6
I/O
P0.5
I/O
AD5
I/O
P0.4
I/O
AD4
I/O
P0.3
I/O
AD3
I/O
P0.2
I/O
AD2
I/O
P0. 1
AD1
P0.0
AD0
VDD
I/O
I/O
I/O
I/O
-
P1.4
44
AD7
P1.5
7
6
P0.3/AD3
13
26
P0.2/AD2
12
25
P0.1/AD1
11
24
P0.0/AD0
4
5
6
7
8
9
10
Function
No Connect
Timer 2 Clock Out
Bit 0 of Port 1
Timer 2 Control
Bit 1 of Port 1
Bit 2 of Port 1
Bit 3 of Port 1
Bit 4 of Port 1
Bit 5 of Port 1
Bit 6 of Port 1
Bit 7 of Port 1
Reset
Receive Data
Bit 0 of Port 3
No Connect
Transmit Data &
Bit 1 of Port 3
External Interrupt 0
Bit 2 of Port 3
External Interrupt 1
Bit 3 of Port 3
Timer 0
Bit 4 of Port 3
Timer 1 & 3
Bit 5 of Port
Ext. Memory Write
Bit 6 of Port 3
Ext. Memory Read
Bit 7 of Port 3
Oscillator/Crystal Output
Oscillator/Crystal In
Ground
No Connect
VDD
3
I/O
I
I/O
I
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I
I
I/O
O
I/O
I
I/O
I
I/O
I
I/O
I
I/O
O
I/O
O
I/O
O
I
-
Function
Bit 0 of Port 2
Bit 8 of External Memory Address
Bit 1 of Port 2
Bit 9 of External Memory Address
Bit 2 of Port 2
Bit 10 of External Memory Address
Bit 3 of Port 2 &
Bit 11 of External Memory Address
Bit 4 of Port 2
Bit 12 of External Memory Address
Bit 5 of Port 2
Bit 13 of External Memory Address
Bit 6 of Port 2
Bit 14 of External Memory Address
Bit 7 of Port 2
Bit 15 of External Memory Address
Program Store Enable
Address Latch Enable
No Connect
External Access
Bit 7 Of Port 0
Data/Address Bit 7 of External
Memory
Bit 6 of Port 0
Data/Address Bit 6 of External
Memory
Bit 5 of Port 0
Data/Address Bit 5 of External
Memory
Bit 4 of Port 0
Data/Address Bit 4 of External
Memory
Bit 3 Of Port 0
Data/Address Bit 3 of External
Memory
Bit 2 of Port 0
Data/Address Bit 2 of External
Memory
Bit 1 of Port 0 & Data
Address Bit 1 of External Memory
Bit 0 Of Port 0 & Data
Address Bit 0 of External Memory
VCC
NC
2
Name
NC
T2
P1.0
T2EX
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
RES
RXD
P3.0
NC
TXD
P3.1
#INT0
P3.2
#INT1
P3.3
T0
P3.4
T1
P3.5
#WR
P3.6
#RD
P3.7
XTAL2
XTAL1
VSS
NC
I/O
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
O
O
I
I/O
T2/P1.0
1
Name
P2.0
A8
P2.1
A9
P2.2
A10
P2.3
A11
P2.4
A12
P2.5
A13
P2.6
A14
P2.7
A15
#PSEN
ALE
NC
#EA
P0.7
P1.2
T2EX/P1.1
PLCC
- 44
P1.3
PLCC
- 44
T ABLE 2: PIN DESCRIPTIONS FOR PLCC-44
40
1
39
P1.6
RESET
RXD/P3.0
P0.7/AD7
#EA
VRS51x540
PLCC-44
NC
TXD/P3.1
#INT0/P3.2
NC
ALE
#PSEN
P2.7/A15
#INT1/P3.3
17
18
29
P2.6/A14
P2.5/A13
P2.4/A12
P2.3/A11
P2.2/A10
P2.1/A9
NC
VSS
P2.0/A8
XTAL1
XTAL2
28
#RD/P3.7
#WR/P3.6
T0/P3.4
T1/P3.5
P0.4/AD4
P0.5/AD5
P0.6/AD6
P1.7
________________________________________________________________________________________________
www.ramtron.com
page 3 of 40
VRS51x540
VRS51x540 DIP-40 Pin Descriptions
T ABLE 3: VRS51X540 IN DESCRIPTIONS FOR DIP-40 PACKAGE
DIP40
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Name
I/O
T2
P1.0
T2EX
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
RESET
RXD
P3.0
TXD
P3.1
#INT0
P3.2
#INT1
P3.3
T0
P3.4
T1
P3.5
#WR
P3.6
#RD
P3.7
XTAL2
XTAL1
VSS
I
I/O
I
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I
I
I/O
O
I/O
I
I/O
I
I/O
I
I/O
I
I/O
O
I/O
O
I/O
O
I
-
Function
Timer 2 Clock Out
Bit 0 of Port 1
Timer 2 Control
Bit 1 of Port 1
Bit 2 of Port 1
Bit 3 of Port 1
Bit 4 of Port 1
Bit 5 of Port 1
Bit 6 of Port 1
Bit 7 of Port 1
Reset
Receive Data
Bit 0 of Port 3
Transmit Data &
Bit 1 of Port 3
External Interrupt 0
Bit 2 of Port 3
External Interrupt 1
Bit 3 of Port 3
Timer 0
Bit 4 of Port 3
Timer 1 & 3
Bit 5 of Port
Ext. Memory Write
Bit 6 of Port 3
Ext. Memory Read
Bit 7 of Port 3
Oscillator/Crystal Output
Oscillator/Crystal In
Ground
T2 / P1.0
1
40
VDD
T2EX / P1.1
2
39
P0.0 / AD0
P1.2
3
38
P0.1 / AD1
P1.3
4
37
P0.2 / AD2
P1.4
5
36
P0.3 / AD3
P1.5
6
35
P0.4 / AD4
P1.6
7
34
P0.5 / AD5
P1.7
8
33
P0.6 / AD6
RESET
9
32
P0.7 / AD7
31
#EA / VPP
RXD / P3.0
10
VRS51x540
DIP-40
TXD / P3.1
11
30
ALE
#INT0 / P3.2
12
29
PSEN
#INT1 / P3.3
13
28
P2.7 / A15
T0 / P3.4
14
27
P2.6 / A14
T1 / P3.5
15
26
P2.5 / A13
#WR / P3.6
16
25
P2.4 / A12
#RD / P3.7
17
24
P2.3 / A11
XTAL2
18
23
P2.2 / A10
XTAL1
19
22
P2.1 / A9
VSS
20
21
P2.0 / A8
DIP40
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Name
I/O
P2.0
A8
P2.1
A9
P2.2
A10
P2.3
A11
P2.4
A12
P2.5
A13
P2.6
A14
P2.7
A15
#PSEN
ALE
#EA /
VPP
P0.7
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
I/O
O
O
O
AD7
I/O
P0.6
I/O
AD6
I/O
P0.5
I/O
AD5
I/O
P0.4
I/O
AD4
I/O
P0.3
I/O
AD3
I/O
P0.2
I/O
AD2
I/O
P0. 1
AD1
P0.0
AD0
VDD
I/O
I/O
I/O
I/O
-
I
I/O
Function
Bit 0 of Port 2
Bit 8 of External Memory Address
Bit 1 of Port 2
Bit 9 of External Memory Address
Bit 2 of Port 2
Bit 10 of External Memory Address
Bit 3 of Port 2 &
Bit 11 of External Memory Address
Bit 4 of Port 2
Bit 12 of External Memory Address
Bit 5 of Port 2
Bit 13 of External Memory Address
Bit 6 of Port 2
Bit 14 of External Memory Address
Bit 7 of Port 2
Bit 15 of External Memory Address
Program Store Enable
Address Latch Enable
External Access
Flash programming voltage input
Bit 7 Of Port 0
Data/Address Bit 7 of External
Memory
Bit 6 of Port 0
Data/Address Bit 6 of External
Memory
Bit 5 of Port 0
Data/Address Bit 5 of External
Memory
Bit 4 of Port 0
Data/Address Bit 4 of External
Memory
Bit 3 Of Port 0
Data/Address Bit 3 of External
Memory
Bit 2 of Port 0
Data/Address Bit 2 of External
Memory
Bit 1 of Port 0 & Data
Address Bit 1 of External Memory
Bit 0 Of Port 0 & Data
Address Bit 0 of External Memory
Supply input
______________________________________________________________________________________________
www.ramtron.com
page 4 of 40
VRS51x540
Instruction Set
Mnemonic
The following tables describe the instruction set of the
VRS51x540. The instructions are functional and binary
code compatible with industry standard 8051s.
T ABLE 4: LEGEND FOR INSTRUCTION SET T ABLE
Symbol
A
Rn
Direct
@Ri
Rel
Bit
#data
#data 16
addr 16
addr 11
Function
Accumulator
Register R0-R7
Internal register address
Internal register pointed to by R0 or R1 (except MOVX)
Two's complement offset byte
Direct bit address
8-bit constant
16-bit constant
16-bit destination address
11-bit destination address
T ABLE 5: VRS51X540 INSTRUCTION SET
Mnemonic
Description
Arithmetic instructions
ADD A, Rn
Add register to A
ADD A, direct
Add direct byte to A
ADD A, @Ri
Add data memory to A
ADD A, #data
Add immediate to A
ADDC A, Rn
Add register to A with carry
ADDC A, direct
Add direct byte to A with carry
ADDC A, @Ri
Add data memory to A with carry
ADDC A, #data
Add immediate to A with carry
SUBB A, Rn
Subtract register from A with borrow
SUBB A, direct
Subtract direct byte from A with borrow
SUBB A, @Ri
Subtract data mem from A with borrow
SUBB A, #data
Subtract immediate from A with borrow
INC A
Increment A
INC Rn
Increment register
INC direct
Increment direct byte
INC @Ri
Increment data memory
DEC A
Decrement A
DEC Rn
Decrement register
DEC direct
Decrement direct byte
DEC @Ri
Decrement data memory
INC DPTR
Increment data pointer
MUL AB
Multiply A by B
DIV AB
Divide A by B
DA A
Decimal adjust A
Logical Instructions
ANL A, Rn
AND register to A
ANL A, direct
AND direct byte to A
ANL A, @Ri
AND data memory to A
ANL A, #data
AND immediate to A
ANL direct, A
AND A to direct byte
ANL direct, #data
AND immediate data to direct byte
ORL A, Rn
OR register to A
ORL A, direct
OR direct byte to A
ORL A, @Ri
OR data memory to A
ORL A, #data
OR immediate to A
ORL direct, A
OR A to direct byte
ORL direct, #data
OR immediate data to direct byte
XRL A, Rn
Exclusive-OR register to A
XRL A, direct
Exclusive-OR direct byte to A
XRL A, @Ri
Exclusive-OR data memory to A
XRL A, #data
Exclusive-OR immediate to A
XRL direct, A
Exclusive-OR A to direct byte
XRL direct, #data
Exclusive-OR immediate to direct byte
CLR A
Clear A
CPL A
Compliment A
SWAP A
Swap nibbles of A
RL A
Rotate A left
RLC A
Rotate A left through carry
RR A
Rotate A right
RRC A
Rotate A right through carry
Size
(bytes)
Instr. Cycles
1
2
1
2
1
2
1
2
1
2
1
2
1
1
2
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
4
4
1
1
2
1
2
2
3
1
2
1
2
2
3
1
2
1
2
2
3
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
2
1
1
1
1
1
2
1
1
1
1
1
1
1
Description
Boolean Instruction
CLR C
Clear Carry bit
CLR bit
Clear bit
SETB C
Set Carry bit to 1
SETB bit
Set bit to 1
CPL C
Complement Carry bit
CPL bit
Complement bit
ANL C,bit
Logical AND between Carry and bit
ANL C,#bit
Logical AND between Carry and not bit
ORL C,bit
Logical ORL between Carry and bit
ORL C,#bit
Logical ORL between Carry and not bit
MOV C,bit
Copy bit value into Carry
MOV bit,C
Copy Carry value into Bit
Data Transfer Instructions
MOV A, Rn
Move register to A
MOV A, direct
Move direct byte to A
MOV A, @Ri
Move data memory to A
MOV A, #data
Move immediate to A
MOV Rn, A
Move A to register
MOV Rn, direct
Move direct byte to register
MOV Rn, #data
Move immediate to register
MOV direct, A
Move A to direct byte
MOV direct, Rn
Move register to direct byte
MOV direct, direct
Move direct byte to direct byte
MOV direct, @Ri
Move data memory to direct byte
MOV direct, #data
Move immediate to direct byte
MOV @Ri, A
Move A to data memory
MOV @Ri, direct
Move direct byte to data memory
MOV @Ri, #data
Move immediate to data memory
MOV DPTR, #data
Move immediate to data pointer
MOVC A, @A+DPTR
Move code byte relative DPTR to A
MOVC A, @A+PC
Move code byte relative PC to A
MOVX A, @Ri
Move external data (A8) to A
MOVX A, @DPTR
Move external data (A16) to A
MOVX @Ri, A
Move A to external data (A8)
MOVX @DPTR, A
Move A to external data (A16)
PUSH direct
Push direct byte onto stack
POP direct
Pop direct byte from stack
XCH A, Rn
Exchange A and register
XCH A, direct
Exchange A and direct byte
XCH A, @Ri
Exchange A and data memory
XCHD A, @Ri
Exchange A and data memory nibble
Branching Instructions
ACALL addr 11
Absolute call to subroutine
LCALL addr 16
Long call to subroutine
RET
Return from subroutine
RETI
Return from interrupt
AJMP addr 11
Absolute jump unconditional
LJMP addr 16
Long jump unconditional
SJMP rel
Short jump (relative address)
JC rel
Jump on carry = 1
JNC rel
Jump on carry = 0
JB bit, rel
Jump on direct bit = 1
JNB bit, rel
Jump on direct bit = 0
JBC bit, rel
Jump on direct bit = 1 and clear
JMP @A+DPTR
Jump indirect relative DPTR
JZ rel
Jump on accumulator = 0
JNZ rel
Jump on accumulator 1= 0
CJNE A, direct, rel
Compare A, direct JNE relative
CJNE A, #d, rel
Compare A, immediate JNE relative
CJNE Rn, #d, rel
Compare reg, immediate JNE relative
CJNE @Ri, #d, rel
Compare ind, immediate JNE relative
DJNZ Rn, rel
Decrement register, JNZ relative
DJNZ direct, rel
Decrement direct byte, JNZ relative
Miscellaneous Instruction
NOP
No operation
Rn:
Any of the register R0 to R7
@Ri:
Indirect addressing using Register R0 or R1
#data: immediate Data provided with Instruction
#data16: Immediate data included with instruction
bit:
address at the bit level
rel:
relative address to Program counter from +127 to –128
Addr11: 11-bit address range
Addr16: 16-bit address range
#d:
Immediate Data supplied with instruction
Size
(bytes)
Instr. Cycles
1
2
1
2
1
2
2
2
2
2
2
2
1
1
1
1
1
1
2
2
2
2
1
2
1
2
1
2
1
2
2
2
2
3
2
3
1
2
2
3
1
1
1
1
1
1
2
2
1
2
1
1
1
1
1
1
1
2
1
1
2
2
2
2
1
2
1
2
2
2
2
2
2
2
2
2
1
1
1
1
2
3
1
1
2
3
2
2
2
3
3
3
1
2
2
3
3
3
3
2
3
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
1
______________________________________________________________________________________________
www.ramtron.com
page 5 of 40
VRS51x540
Special Function Registers (SFR)
Addresses 80h to FFh of the SFR address space can be accessed in direct addressing mode only. The following table
lists the VRS51x540 Special Function Registers.
T ABLE 6: SPECIAL FUNCTION REGISTERS (SFR)
SFR
Register
P0
SP
DPL
DPH
Reserved
PCON
TCON
TMOD
TL0
TL1
TH0
TH1
P1
SCON
SBUF
WDTCON
P2
IE
P3
IP
SYSCON
T2CON
RCAP2L
RCAP2H
TL2
TH2
PSW
ACC
B
SFR
Adrs
80h
81h
82h
83h
84h
87h
88h
89h
8Ah
8Bh
8Ch
8Dh
90h
98h
99h
9Fh
A0h
A8h
B0h
B8h
BFh
C8h
CAh
CBh
CCh
CDh
D0h
E0h
F0h
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
SMOD
TF1
GATE1
SM0
WDTE
EA
WDRESET
TF2
-
TR1
C/T1
SM1
EXF2
-
TF0
M1.1
SM2
WDCLR
ET2
PT2
RCLK
-
TR0
M0.1
REN
ES
PS
TCLK
-
GF1
IE1
GATE0
TB8
ET1
PT1
EXEN2
-
GF0
IT1
C/T0
RB8
WDPS2
EX1
PX1
PDOWN
IE0
M1.0
TI
WDPS1
ET0
PT0
TR2
-
C/T2
-
IDLE
IT0
M0.0
RI
WDPS0
EX0
PX0
ALEI
CP/RL2
-
CY
-
AC
-
F0
-
RS1
-
RS0
-
OV
-
-
P
-
Reset Value
00000000b
00000000b
00000000b
00000000b
0*0**000b
00000000b
00000000b
0*****00b
00000000b
00000000b
00000000b
00000000b
00000000b
00000000b
______________________________________________________________________________________________
www.ramtron.com
page 6 of 40
VRS51x540
Program Memory Structure
Data Memory
Program Memory
The VRS51x540 includes 4k of on-chip Program Flash
memory.
The VRS51x540 has a total of 128 Bytes of RAM
memory configured as the internal memory structure of
a standard 8051.
FIGURE 4: VRS51X540 DATA MEMORY
FIGURE 3: VRS51X540 INTERNAL PROGRAM MEMORY
FFFh
FFh
80h
7Fh
VRS51x540
Flash Memory
(4K Bytes)
00h
0000h
Program Status Word Register
The PSW register is a bit addressable register that
contains the status flags (CY, AC, OV, P), user flag
(F0) and register bank select bits (RS1, RS0) of the
8051 processor.
T ABLE 7: PROGRAM STATUS WORD REGISTER (PSW) - SFR DOH
7
CY
Bit
7
6
5
4
3
2
1
0
RS1
0
0
1
1
6
AC
5
F0
Mnemonic
CY
AC
F0
RS1
RS0
OV
P
RS0
0
1
0
1
4
RS1
3
RS0
2
OV
1
-
0
P
Description
Carry Bit
Auxiliary Carry Bit from bit 3 to 4.
User flag
R0-R7 Registers bank select bit 0
R0-R7 Registers bank select bit 1
Overflow flag
Parity flag
Active Bank
0
1
2
3
Address
00h-07h
08h-0Fh
10h-17h
18-1Fh
128 bytes RAM
(indirect addressing only)
128 bytes RAM
(Can be accessed in indirect and
direct addressing mode)
Lower 128 bytes (00h to 7Fh, Bank 0 & Bank 1)
The lower 128 bytes of data memory (from 00h to 7Fh)
is summarized as follows:
• Address range 00h to 7Fh can be accessed in
direct and indirect addressing modes.
• Address range 00h to 1Fh includes R0-R7
registers area.
• Address range 20h to 2Fh is bit addressable.
• Address range 30h to 7Fh is not bit addressable
and can be used as general-purpose storage.
.
FIGURE 5: VRS51X540 INTERNAL RAM STRUCTURE
FFh
SFR Area
Direct or Bit Access Only
DPH
DPL
SP
P0
The VRS51x540 has one 16-bit data pointer. The
DPTR is accessed through two SFR addresses: DPL
located at address 82h and DPH located at address
83h.
87
86
85
84
83
82
81
80
80h
7Fh
80 Bytes of
General Purpose RAM
30h
2Fh
20h
Data Pointer
SFR
(Direct addressing mode only)
18h
10h
08h
00h
7F
7E
7D
7C
7B
7A
79
78
77
76
75
74
73
72
71
70
0F
0E
0D
0C
0B
0A
09
08
07
06
05
04
03
02
01
00
R7
R0
R7
R0
R7
R0
R7
R0
Registers Bank 3
Registers Bank 2
Registers Bank 1
Registers Bank 0
______________________________________________________________________________________________
www.ramtron.com
page 7 of 40
VRS51x540
These power saving modes are controlled by the
PDOWN and IDLE bits of the PCON register at
address 87h.
Description of Peripherals
System Control Register
The SYSCON Register is used for system control and
is described in the following table. The WDRESET bit
(7) indicates whether the system has been reset due to
the overflow of the Watchdog Timer.
Bit 0 of the SYSCON register is the ALE output inhibit
bit. Setting this bit to a 1 will inhibit the Fosc/6 clock
signal output to the ALE pin.
T ABLE 9: POWER CONTROL REGISTER (PCON) - SFR 87H
7
Bit
7
6
Mnemonic
SMOD
7
6
5
Bit
7
Mnemonic
6
5
4
3
2
1
0
Unused
Unused
Unused
Unused
Unused
Unused
ALEI
WDRESET
4
3
Unused
2
1
XRAME
0
ALEI
Description
This is the Watchdog Timer reset bit. It
will be set to 1 when the reset signal
generated by WDT overflows.
ALE output inhibit bit, which is used to
reduce EMI.
3
2
1
RAM1
0
RAM0
Description
1: Double the baud rate of the serial port
frequency that was generated by Timer 1.
0: Normal serial port baud rate generated by
Timer 1.
T ABLE 8: SYSTEM CONTROL REGISTER (SYSCON) – SFR BFH
WDRESET
5
4
Unused
6
5
4
3
2
1
0
GF1
GF0
PDOWN
IDLE
General Purpose Flag
General Purpose Flag
Power down mode control bit
Idle mode control bit
Power Control Register
The VRS51x540 provides two power saving modes:
Idle and Power Down. These two modes serve to
reduce the power consumption of the device.
In Idle mode, the processor is stopped but the oscillator
continues to run. The content of the RAM, I/O state
and SFR registers are maintained and the Timer and
external interrupts are left operational. The processor
will be woken up when an external event, triggering an
interrupt, occurs.
In Power Down mode, the oscillator and peripherals of
the VRS51x540 are disabled. The contents of the
RAM and the SFR registers, however, are maintained.
The minimum VCC in Power Down mode is 2V.
______________________________________________________________________________________________
www.ramtron.com
page 8 of 40
VRS51x540
Input/Output Ports
The VRS51x540 has a total of 32 bi-directional I/O
lines grouped into four 8-bit I/O ports. These I/Os can
be individually configured as inputs or outputs.
FIGURE 6: INTERNAL STRUCTURE OF ONE OF THE FOUR I/O PORT LINES
Read Register
With the exception of the P0 I/Os, which are of the
open drain type, each I/O is made of a transistor
connected to ground and a weak pull-up resistor.
Internal Bus
Writing a 0 in a given I/O port bit register will activate
the transistor connected to Vss, this will bring the I/O to
a LOW level.
Writing a 1 into a given I/O port bit register de-activates
the transistor between the pin and ground. In this case
the pull-up resistor will bring the corresponding pin to a
HIGH level.
To use a given I/O as an input, a 1 must be written into
its associated port register bit. By default, upon reset
all I/Os are configured as inputs.
General Structure of an I/O Port
The following elements establish the link between the
core unit and the pins of the microcontroller:
• Special Function Register (same name as port)
• Output Stage Amplifier (the structure of this
element varies with its auxiliary function)
From the next figure, one can see that the D flip-flop
stores the value received from the internal bus after
receiving a write signal from the core. Also, note that
the Q output of the flip-flop can be linked to the internal
bus by executing a read instruction.
This is how one would read the content of the register.
It is also possible to link the value of the pin to the
internal bus. This is done by the “read pin” instruction.
In short, the user may read the value of the register or
the pin.
Q
D Flip-Flop
Write to
Register
Output
Stage
IC Pin
Q
Read Pin
Structure of the P1, P2, P3
The following figure gives a general idea of the
structure P1, P2 and P3 ports. Note that the figure
below does not show the intermediary logic that
connects the output of the register and the output stage
together because this logic varies with the auxiliary
function of each port.
FIGURE 7: GENERAL STRUCTURE OF THE O UTPUT STAGE OF P1, P2 AND P3
Read Register
Vcc
Pull-up
Network
Internal Bus
Q
IC Pin
D Flip-Flop
Write to
Register
Q
X1
Read Pin
Each line may be used independently as a logical
input or output. When used as an input, as mentioned
earlier, the corresponding port register bit must be
high.
______________________________________________________________________________________________
www.ramtron.com
page 9 of 40
VRS51x540
Structure of Port 0
Port P0 and P2 as Address and Data Bus
The internal structure of P0 is shown below. The
auxiliary function of this port requires a particular logic.
As opposed to the other ports, P0 is truly bi-directional.
In other words, when used as an input, it is considered
to be in a floating logical state (high impedance state).
This arises from the absence of the internal pull-up
resistance. The pull-up resistance is actually replaced
by a transistor that is only used when the port is
configured to access the external memory/data bus
(EA=0).
The output stage may receive data from two sources
When used as an I/O port, P0 acts as an open drain
port and the use of an external pull-up resistor is likely
to be required for most applications.
•
The outputs of register P0 or the bus address
itself, multiplexed with the data bus for P0.
•
The outputs of the P2 register or the high byte
(A8 through A15) of the bus address for the P2
port.
FIGURE 9: P2 PORT STRUCTURE
Read Register
Vcc
Address
Pull-up
Network
FIGURE 8: PORT P0’ S PARTICULAR STRUCTURE
Q
Internal Bus
IC Pin
D Flip-Flop
Address A0/A7
Read Register
Write to
Register
Control
X1
Q
Control
Vcc
Internal Bus
Read Pin
Q
IC Pin
D Flip-Flop
Write to
Register
Q
X1
Read Pin
When P0 is used as an external memory bus input (for
a MOVX instruction, for example), the outputs of the
register are automatically forced to 1.
When the ports are used as an address or data bus,
the special function registers P0 and P2 are
disconnected from the output stage. The 8-bits of the
P0 register are forced to 1 and the content of the P2
register remains constant.
Auxiliary Port 1 Functions
The port 1 I/O pins are shared with the Timer 2 EX and
T2 inputs as shown below:
Pin
P1.0
P1.1
P1.2
Mnemonic
T2
T2EX
Function
Timer 2 counter input
Timer2 Auxiliary input
P1.3
P1.4
P1.5
P1.6
P1.7
______________________________________________________________________________________________
www.ramtron.com
page 10 of 40
VRS51x540
Auxiliary P3 Port Functions
Software Particularities Concerning the Ports
The Port 3 I/O pins are shared with the UART
interface, INT0 and INT1 interrupts, Timer 0 and Timer
1 inputs and finally the #WR and #RD lines when
external memory access is performed.
Some instructions allow the user to read the logic state
of the output pin, while others allow the user to read
the content of the associated port register. These
instructions are called read-modify-write instructions. A
list of these instructions may be found in the table
below.
FIGURE 10: P3 PORT STRUCTURE
Auxiliary
Function: Output
Read Register
Vcc
IC Pin
Q
Internal Bus
X1
D Flip-Flop
Write to
Register
Q
Read Pin
Auxiliary
Function: Input
The following table describes the auxiliary function of
the port 3 I/O pins.
T ABLE 10: P3 AUXILIARY F UNCTION T ABLE
Pin
P3.0
P3.1
P3.2
P3.3
Mnemonic
RXD
TXD
INT0
INT1
P3.4
P3.5
P3.6
T0
T1
P3.7
RD
WR
Function
Serial Port:
Receive data in asynchronous
mode. Input and output data in
synchronous mode.
Serial Port:
Transmit data in asynchronous
mode. Output clock value in
synchronous mode.
External Interrupt 0
Timer 0 Control Input
External Interrupt 1
Timer 1 Control Input
Timer 0 Counter Input
Timer 1 Counter Input
Write signal for external memory
Read signal for external memory
Upon execution of these instructions, the content of the
port register (at least 1-bit) is modified. The other read
instructions take the present state of the input into
account. For example, the instruction ANL P3, #01h
obtains the value in the P3 register; performs the
desired logic operation with the constant 01h; and recopies the result into the P3 register. When users want
to take the present state of the inputs into account,
they must first read these states and perform an AND
operation between the reading and the constant.
MOV A, P3; State of the inputs in the accumulator
ANL A, #01; AND operation between P3 and 01h
When the port is used as an output, the register
contains information on the state of the output pins.
Measuring the state of an output directly on the pin is
inaccurate because the electrical level depends mostly
on the type of charge that is applied to it. The functions
shown below take the value of the register rather than
that of the pin.
T ABLE 11: LIST OF INSTRUCTIONS THAT READ AND MODIFY THE PORT USING REGISTER
VALUES
Instruction
ANL
ORL
XRL
JBC
CPL
INC
DEC
DJNZ
MOV P., C
CLR P.x
SETB P.x
Function
Logical AND ex: ANL P0, A
Logical OR ex: ORL P2, #01110000B
Exclusive OR ex: XRL P1, A
Jump if the bit of the port is set to 0
Complement one bit of the port
Increment the port register by 1
Decrement the port register by 1
Decrement by 1 and jump if the result
is not equal to 0
Copy the held bit C to the port
Set the port bit to 0
Set the port bit to 1
______________________________________________________________________________________________
www.ramtron.com
page 11 of 40
VRS51x540
Port Operation Timing
Writing to a Port (Output)
When an operation results in a modification of the
content in a port register, the new value is placed at the
output of the D flip-flop during the T12 period of the last
machine cycle that the instruction needed to execute.
It is important to note, however, that the output stage
only samples the output of the registers on the P1
phase of each period. It follows the new value
appearing at the output after the T12 period of the
following machine cycle.
Reading a Port (Input)
The reading of an I/O pin takes place:
• During T9 cycle for P0, P1
• During T10 cycle for P2, P3
• When the ports are configured as I/Os
•
In order to be sampled, the signal duration present on
the I/O inputs must be longer than Fosc/12.
I/O Ports Driving Capability
The maximum allowable continuous current that the
device can sink on an I/O port is defined by the
following:
Maximum sink current on one given I/O
Maximum total sink current for P0
Maximum total sink current for P1, 2, 3
Maximum total sink current on all I/O
10mA
26mA
15mA
71mA
It is not recommended to exceed the sink current
outlined in the above table. Doing so is likely to make
the low-level output voltage exceed the device’s
specification and it is likely to affect device reliability.
The VRS51x540 I/O ports are not designed to source
current.
______________________________________________________________________________________________
www.ramtron.com
page 12 of 40
VRS51x540
Timers
The VRS51x540 includes three 16-bit timers: T0, T1
and T2.
The timers can operate in two specific modes:
• Event counting mode
• Timer mode
When operating in counting mode, the counter is
incremented each time an external event, such as a
transition in the logical state of the timer input (T0, T1,
T2 input), is detected. When operating in timer mode,
the counter is incremented by the microcontroller’s
direct clock pulse or by a divided version of this pulse.
Timer 0 and Timer 1
Timers 0 and 1 have four modes of operation. These
modes allow the user to change the size of the
counting register or to authorize an automatic reload
when provided with a specific value. Timer 1 can also
be used as a baud rate generator to generate
communication frequencies for the serial interface.
Timer 1 and Timer 0 are configured by the TMOD and
TCON registers.
T ABLE 12: T IMER MODE CONTROL REGISTER (TMOD) – SFR 89H
7
GATE
6
C/T
5
M1
Bit
7
Mnemonic
GATE1
6
C/T1
5
4
3
M1.1
M0.1
GATE0
2
C/T0
1
0
M1.0
M0.0
4
M0
3
GATE
2
C/T
1
M1.0
0
M0.0
Description
1: Enables external gate control (pin INT1 for
Counter 1). When INT1 is high, and TRx bit is
set (see TCON register), a counter is
incremented every falling edge on the T1IN
input pin.
Selects timer or counter operation (Timer 1).
1 = A counter operation is performed
0 = The corresponding register will function
as a timer.
Selects mode for Timer/Counter 1
Selects mode for Timer/Counter 1
If set, enables external gate control (pin INT0
for Counter 0). When INT0 is high, and TRx
bit is set (see TCON register), a counter is
incremented every falling edge on the T0IN
input pin.
Selects timer or counter operation (Timer 0).
1 = A counter operation is performed
0 = The corresponding register will function
as a timer.
Selects mode for Timer/Counter 0.
Selects mode for Timer/Counter 0.
The table below summarizes the four modes of
operation of timers 0 and 1. The timer-operating mode
is selected by the bits M1 and M0 of the TMOD
register.
T ABLE 13: T IMER/COUNTER MODE DESCRIPTION SUMMARY
M1
M0
Mode
Function
0
0
1
0
1
0
Mode 0
Mode 1
Mode 2
1
1
Mode 3
13-bit Counter
16-bit Counter
8-bit auto-reload Counter/Timer. The reload
value is kept in TH0 or TH1, while TL0 or TL1
is incremented every machine cycle. When TLx
overflows, the value of THx is copied to TLx.
If Timer 1 M1 and M0 bits are set to 1, Timer 1
stops.
______________________________________________________________________________________________
www.ramtron.com
page 13 of 40
VRS51x540
Timer 0/ Timer 1 Counter / Timer Functions
Operating Modes
Timing Function
The user may change the operating mode by varying
the M1 and M0 bits of the TMOD SFR.
When operating as a timer, the counter is automatically
incremented at every system cycle (Fosc/12). A flag is
raised in the event that an overflow occurs and the
counter acquires a value of zero. These flags (TF0 and
TF1) are located in the TCON register.
T ABLE 14: T IMER 0 AND 1 CONTROL REGISTER (TCON) –SFR 88H
7
6
5
4
3
2
1
0
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Bit
7
Mnemonic
TF1
Description
Timer 1 Overflow Flag. Set by hardware on
Timer/Counter overflow. Cleared by
hardware on Timer/Counter overflow.
Cleared by hardware when processor
vectors to interrupt routine.
6
TR1
5
TF0
Timer 1 Run Control Bit. Set/cleared by
software to turn Timer/Counter on or off.
Timer 0 Overflow Flag. Set by hardware on
Timer/Counter overflow. Cleared by
hardware when processor vectors to
interrupt routine.
Timer 0 Run Control Bit. Set/cleared by
software to turn Timer/Counter on or off.
Interrupt Edge Flag. Set by hardware when
external interrupt edge is detected. Cleared
when interrupt processed.
Interrupt 1 Type Control Bit. Set/cleared by
software to specify falling edge/low level
triggered external interrupts.
Interrupt 0 Edge Flag. Set by hardware
when external interrupt edge is detected.
Cleared when interrupt processed.
Interrupt 0 Type control bit. Set/cleared by
software to specify falling edge/low level
triggered external interrupts.
4
TR0
3
IE1
2
IT1
1
IE0
0
IT0
Counting Function
When operating as a counter, the timer’s register is
incremented at every falling edge of the T0, T1 and T2
signals located at the input of the timer. In this case,
the signal is sampled at the T10 phase of each
machine cycle for Timer 0, Timer 1 and T9 for Timer 2.
When the sampler sees a high immediately followed by
a low in the next machine cycle, the counter is
incremented. Two system cycles are required to detect
and record an event. This reduces the counting
frequency by a factor of 24 (24 times less than the
oscillator’s frequency).
Mode 0
A schematic representation of this mode of operation
can be found in Figure 11. From the figure, we notice
that the timer operates as an 8-bit counter preceded by
a divide-by-32 prescaler composed of the 5 LSBs of
TL1. The register of the counter is configured to be 13
bits long. When an overflow causes the value of the
register to roll over to 0, the TFx interrupt signal goes
to 1. The count value is validated as soon as TRx goes
to 1 and the GATE bit is 0, or when INTx is 1.
FIGURE 11: T IMER/COUNTER 1 MODE 0: 13-BIT COUNTER
CLK
÷12
0
TL1
C/T =0
CLK
1
T1PIN
0
4
7
Mode 0
C/T =1
Control
Mode 1
TR1
GATE
0
TH1
7
INT1 PIN
TF1
INT
Mode 1
Mode 1 is almost identical to Mode 0. They differ in that
in Mode 1, the counter uses the full 16-bits and has no
prescaler.
Mode 2
In this mode, the register of the timer is configured as
an 8-bit automatically re-loadable counter. In Mode 2, it
is the lower byte TLx that is used as the counter. In the
event of a counter overflow, the TFx flag is set to 1 and
the value contained in THx, which is preset by
software, is reloaded into the TLx counter. The value of
THx remains unchanged.
______________________________________________________________________________________________
www.ramtron.com
page 14 of 40
VRS51x540
FIGURE 12: T IMER/COUNTER 1 MODE 2: 8-BIT AUTOMATIC RELOAD
CLK
÷12
0
C/T =0
1
C/T=1
TL1
0
7
Control
T1 Pin
Reload
0
7
TH1
TR1
GATE
TF1
INT
INT0 PIN
Mode 3
In Mode 3, Timer 1 is blocked as if its control bit, TR1,
was set to 0. In this mode, Timer 0’s registers TL0 and
TH0 are configured as two separate 8-bit counters.
Also, the TL0 counter uses Timer 0’s control bits C/T,
GATE, TR0, INT0, TF0 and the TH0 counter is held in
Timer Mode (counting machine cycles) and gains
control over TR1 and TF1 from Timer 1. At this point,
TH0 controls the Timer 1 interrupt.
FIGURE 13: T IMER/COUNTER 0 MODE 3
TH0
CLK
0
7
Control
TF1
TR1
CLK
0
TL0
C/T =0
CLK
1
T0PIN
INTERRUPT
÷12
0
7
C/T =1
Control
TF0
INTERRUPT
TR0
GATE
INT0 PIN
______________________________________________________________________________________________
www.ramtron.com
page 15 of 40
VRS51x540
0
Timer 2
Timer 2 of the VRS51x540 is a 16-bit Timer/Counter.
Similar to timers 0 and 1, Timer 2 can operate either as
an event counter or as a timer. The user may switch
functions by writing to the C/T2 bit located in the
T2CON special function register. Timer 2 has three
operating modes: “Auto-Load” “Capture”, and “Baud
Rate Generator”. The T2CON SFR configures the
modes of operation of Timer 2. The following table
describes each bit in the T2CON special function
register.
T ABLE 15: T IMER 2 CONTROL REGISTER (T2CON) –SFR C8H
7
6
5
4
3
2
1
0
TF2
EXF2
RCLK
TCLK
EXEN2
TR2
C/T2
CP/RL2
Bit
Mnemonic
7
TF2
6
5
4
3
2
Capture/Reload Select.
1: Capture of Timer 2 value into RCAP2H,
RCAP2L is performed if EXEN2=1 and a
negative transitions occurs on the T2EX
pin. The capture mode requires RCLK and
TCLK to be 0.
CP/RL2
EXF2
RCLK
TCLK
EXEN2
TR2
1
C/T2
Description
Timer 2 Overflow Flag: Set by an overflow
of Timer 2 and must be cleared by
software. TF2 will not be set when either
RCLK =1 or TCLK =1.
Timer 2 external flag change in state occurs
when either a capture or reload is caused
by a negative transition on T2EX and
EXEN2=1. When Timer 2 is enabled,
EXF=1 will cause the CPU to Vector to the
Timer 2 interrupt routine. Note that EXF2
must be cleared by software.
Serial Port Receive Clock Source.
1: Causes Serial Port to use Timer 2
overflow pulses for its receive clock in
modes 1 and 3.
0: Causes Timer 1 overflow to be used for
the Serial Port receive clock.
Serial Port Transmit Clock.
1: Causes Serial Port to use Timer 2
overflow pulses for its transmit clock in
modes 1 and 3.
0: Causes Timer 1 overflow to be used for
the Serial Port transmit clock.
Timer 2 External Mode Enable.
1: Allows a capture or reload to occur as a
result of a negative transition on T2EX if
Timer 2 is not being used to clock the Serial
Port.
0: Causes Timer 2 to ignore events at
T2EX.
Start/Stop Control for Timer 2.
1: Start Timer 2
0: Stop Timer 2
Timer or Counter Select (Timer 2)
1: External event counter falling edge
triggered.
0: Internal Timer (OSC/12)
0: Auto-reload reloads will occur either with
Timer 2 overflows or negative transitions at
T2EX when EXEN2=1. When either RCK
=1 or TCLK =1, this bit is ignored and the
timer is forced to auto-reload on Timer 2
overflow.
As shown below, there are different possible
combinations of control bits that may be used for the
mode selection of Timer 2.
T ABLE 16: T IMER 2 MODE SELECTION BITS
RCLK + TCLK
CP/RL2
TR2
0
0
1
0
1
1
1
X
1
X
X
0
MODE
16-bit AutoReload Mode
16-bit Capture
Mode
Baud Rate
Generator Mode
Off
The details of each mode are described as follows.
Capture Mode
In Capture Mode the EXEN2 bit value defines if the
external transition on the T2EX pin will be able to
trigger the capture of the timer value.
When EXEN2 = 0, Timer 2 acts as a 16-bit timer or
counter, which, upon overflowing, will set bit TF2
(Timer 2 overflow bit). This overflow can be used to
generate an interrupt.
FIGURE 14: T IMER 2 IN CAPTURE MODE
FOSC
÷12
0
TIMER
0
TL2
TH2
7
0
7
0
7
C/T2
1
COUNTER
T2 Pin
0
RCAP2L
RCAP2H
7
TR2
TF2
T2 EX Pin
EXF2
EXEN2
Timer 2
Interrupt
______________________________________________________________________________________________
www.ramtron.com
page 16 of 40
VRS51x540
When EXEN2 = 1, the above still applies. Additionally,
it is possible to allow a 1 to 0 transition at the T2EX
input to cause the current value stored in the Timer 2
registers (TL2 and TH2) to be captured by the RCAP2L
and RCAP2H registers. Furthermore, the transition at
T2EX causes bit EXF2 in T2CON to be set, and EXF2,
like TF2, can generate an interrupt. Note that both
EXF2 and TF2 share the same interrupt vector.
FOSC
÷2
0
TIMER
TL2
0
0
7
0
7
1
COUNTER
T2 Pin
0
RCAP2L
RCAP2H
7
TR2
1
0
0
Timer 1 Overflow
÷2
Auto-Reload Mode
T2 EX Pin
TCLK
÷16
TX Clock
÷16
RX Clock
1
0
1
SMOD
In this mode, there are also two options. The user may
choose either option by writing to bit EXEN2 in T2CON.
TH2
7
C/T2
RCLK
EXF2
Timer 2
Interrupt
Request
EXEN2
If EXEN2 = 0, when Timer 2 rolls over, it not only sets
TF2, but also causes the Timer 2 registers to be
reloaded with the 16-bit value in the RCAP2L and
RCAP2H registers previously initialised. In this mode,
Timer 2 can be used as a baud rate generator source
for the serial port.
If EXEN2=1, then Timer 2 still performs the above
operation, but a 1 to 0 transition at the external T2EX
input will also trigger an anticipated reload of the Timer
2 with the value stored in RCAP2L, RCAP2H and set
EXF2.
FIGURE 15: T IMER 2 IN AUTO-RELOAD MODE
FOSC
÷12
0
TIMER
0
TL2
TH2
7
0
7
0
7
C/T2
1
COUNTER
T2 Pin
0
RCAP2L
RCAP2H
7
TR2
TF2
T2 EX Pin
EXF2
EXEN2
Timer 2
Interrupt
Baud Rate Generator Mode
The baud rate generator mode is activated when RCLK
is set to 1 and/or TCLK is set to 1. This mode will be
described in the serial port section.
FIGURE 16: T IMER 2 IN AUTOMATIC BAUD GENERATOR MODE
______________________________________________________________________________________________
www.ramtron.com
page 17 of 40
VRS51x540
2
Serial Port
The serial port included in the VRS51x540 can operate
in full duplex; in other words, it can transmit and
receive data simultaneously. This occurs at the same
speed if one timer is assigned as the clock source for
both transmission and reception, and at different
speeds if transmission and reception are each
controlled by their own timer.
The serial port receive is buffered, which means that it
can begin reception of a byte even if the one previously
received byte has not been retrieved from the receive
register by the processor. However, if the first byte still
has not been read by the time reception of the second
byte is complete, the byte present in the receive buffer
will be lost.
The SBUF register provides access to the transmit and
receive registers of the serial port. Reading from the
SBUF register will access the receive register, while a
write to the SBUF loads the transmit register.
1
0
th
RB8
9 data bit received in modes 2 and 3.
TI
In Mode 1, if SM2 = 0, RB8 is the stop bit
that was received.
In Mode 0, this bit is not used.
This bit must be cleared by software.
Transmission Interrupt flag.
RI
Automatically set to 1 when:
th
• The 8 bit has been sent in Mode 0.
• Automatically set to 1 when the stop bit
has been sent in the other modes.
This bit must be cleared by software.
Reception Interrupt flag
Automatically set to 1 when:
th
• The 8 bit has been received in Mode 0.
• Automatically set to 1 when the stop bit
has been sent in the other modes (see
SM2 exception).
This bit must be cleared by software.
T ABLE 18: SERIAL PORT MODES OF OPERATION
SM0
SM1
Mode
Description
Baud Rate
0
0
1
0
1
0
0
1
2
Shift Register
8-bit UART
9-bit UART
1
1
3
9-bit UART
Fosc/12
Variable
Fosc/64 or
Fosc/32
Variable
Serial Port Control Register
The SCON (serial port control) register contains control
and status information, and includes the 9th data bit for
transmit/receive (TB8/RB8 if required), mode selection
bits and serial port interrupt bits (TI and RI).
T ABLE 17: SERIAL PORT CONTROL REGISTER (SCON) – SFR 98H
7
6
5
4
3
2
1
0
SM0
SM1
SM2
REN
TB8
RB8
TI
RI
Bit
7
Mnemonic
SM0
6
SM1
5
SM2
Description
Bit to select mode of operation (see table
below)
Bit to select mode of operation (see table
below)
Multiprocessor communication is possible
in modes 2 and 3.
Modes of Operation
The VRS51x540 serial port can operate in four different
modes. In all four modes, a transmission is initiated by
an instruction that uses the SBUF SFR as a destination
register. In Mode 0, reception is initiated by setting RI
to 0 and REN to 1. An incoming start bit initiates
reception in the other modes provided that REN is set
to 1. The following paragraphs describe the four
modes.
In modes 2 or 3 if SM2 is set to 1, RI will
th
not be activated if the received 9 data bit
(RB8) is 0.
4
REN
3
TB8
In Mode 1, if SM2 = 1 then RI will not be
activated if a valid stop bit was not
received.
Serial Reception Enable Bit
This bit must be set by software and
cleared by software.
1: Serial reception enabled
0: Serial reception disabled
th
9 data bit transmitted in modes 2 and 3
This bit must be set by software and
cleared by software.
______________________________________________________________________________________________
www.ramtron.com
page 18 of 40
VRS51x540
Mode 0
In this mode, the serial data exits and enters through
the RXD pin. TXD is used to output the shift clock. The
signal is composed of 8 data bits starting with the LSB.
The baud rate in this mode is 1/12 the oscillator
frequency.
The SEND signal enables the output of the shift
register to the alternate output function line of P3.0 and
enables SHIFT CLOCK to the alternate output function
line of P3.1. SHIFT CLOCK is high during T11, T12
and T1, T2 and T3, T4 of every machine cycle and low
during T5, T6, T7, T8, T9 and T10. At T12 of every
machine cycle in which SEND is active and the
contents of the transmit shift register are shifted to the
right by one position.
Internal Bus
1
Write to
SBUF
Q
S
SBUF
RXD P3.0
D
Shift
CLK
ZERO DETECTOR
Shift
Clock
TXD P3.1
Shift
Start
TX Control Unit
TX Clock
Fosc/12
Send
TI
Serial Port
Interrupt
RI
RX Clock
Receive
Reception in Mode 0
RX Control Unit
RI
REN
Start Shift 1
RXD P3.0
Input Function
1
1
1
1
1
1
Shift Register
SBUF
Zeros come in from the left as data bits shift out to the
right. The TX control block sends its final shift and deactivates SEND while setting T1 after one condition is
fulfilled: When the MSB of the data byte is at the output
position of the shift register; the 1 that was initially
loaded into the 9th position is just to the left of the MSB;
and all positions to the left of that contain zeros. Once
these conditions are met, the de-activation of SEND
and the setting of T1 occur at T1 of the 10th machine
cycle after the “write to SBUF” pulse.
0
RXD P3.0
READ SBUF
Internal Bus
FIGURE 17: SERIAL PORT MODE 0 BLOCK DIAGRAM
Transmission in Mode 0
Any instruction that uses SBUF as a destination
register may initiate a transmission. The “write to
SBUF” signal also loads a 1 into the 9th position of the
transmit shift register and tells the TX control block to
begin a transmission. The internal timing is such that
one full machine cycle will elapse between a write to
SBUF instruction and the activation of SEND.
When REN and R1 are set to 1 and 0 respectively,
reception is initiated. The bits 11111110 are written to
the receive shift register at T12 of the next machine
cycle by the RX control unit. In the following phase, the
RX control unit will activate RECEIVE.
SHIFT CLOCK to the alternate output function line of
P3.1 is enabled by RECEIVE. At every machine cycle,
SHIFT CLOCK makes transitions at T5 and T11. The
contents of the receive shift register are shifted one
position to the left at T12 of every machine in which
RECEIVE is active. The value that comes in from the
right is the value that was sampled at the P3.0 pin at
T10 of the same machine cycle.
1’s are shifted out to the left as data bits are shifted in
from the right. The RX control block is flagged to do
one last shift and load SBUF when the 0 that was
initially loaded into the rightmost position arrives at the
leftmost position in the shift register.
______________________________________________________________________________________________
www.ramtron.com
page 19 of 40
VRS51x540
Mode 1
For an operation in Mode 1, 10 bits are transmitted
through TXD or received through RXD. The
transactions are composed of: a Start bit (Low), 8 data
bits (LSB first) and one Stop bit (high). The reception is
completed once the Stop bit sets the RB8 flag in the
SCON register. Either Timer 1 or Timer 2 controls the
baud rate in this mode.
The following diagram shows the serial port structure
when configured in Mode 1.
FIGURE 18: SERIAL PORT MODE 1 AND 3 BLOCK DIAGRAM
Internal Bus
When a transmission begins, it places the start bit at
TXD. Data transmission is activated one bit time later.
This activation enables the output bit of the transmit
shift register to TXD. One bit time after that, the first
shift pulse occurs.
In this mode, zeros are clocked in from the left as data
bits are shifted out to the right. When the most
significant bit of the data byte is at the output position
of the shift register, the 1 that was initially loaded into
the 9th position is to the immediate left of the MSB, and
all positions to the left of that contain zeros. This
condition flags the TX Control Unit to shift one more
time.
Reception in Mode 1
1
Write to
SBUF
Timer 1
Overflow
Q
S
SBUF
TXD
D
CLK
Timer 2
Overflow
÷2
ZERO DETECTOR
0 1
SMOD
0
Shift
Start
1
÷16
0
Data
TX Control Unit
TCLK
TX Clock
Send
TI
1
RCLK
÷16
Serial Port
Interrupt
RX Clock
1-0 Transition
Detector
RXD
Start
RI
Load
SBUF
RX Control Unit
Bit
Detector
SHIFT
9-Bit Shift Register
Shift
LOAD SBUF
SBUF
READ SBUF
One to zero transitions at RXD initiates reception. It is
for this reason that RXD is sampled at a rate of 16
multiplied by the baud rate that has been established.
When a transition is detected, 1FFh is written into the
input shift register and the divide-by-16 counter is
immediately reset. The divide-by-16 counter is reset in
order to align its rollovers with the boundaries of the
incoming bit times.
In total, there are 16 states in the counter. During the
7th, 8th and 9th counter states of each bit time; the bit
detector samples the value of RXD. The accepted
value is the value that was seen in at least two of the
three samples. The purpose of doing this is for noise
rejection. If the value accepted during the first bit time
is not zero, the receive circuits are reset and the unit
goes back to searching for another one to zero
transition. Doing this rejects all false start bits. If the
start bit is valid, it is shifted into the input shift register,
and the reception of the rest of the frame will proceed.
Internal Bus
Transmission in Mode 1
Transmission is initiated by any instruction that makes
use of SBUF as a destination register. The 9th bit
position of the transmit shift register is loaded by the
“write to SBUF” signal. This event also flags the TX
Control Unit that a transmission has been requested.
It is after the next rollover in the divide-by-16 counter
when transmission actually begins at T1 of the
machine cycle. It follows that the bit times are
synchronized to the divide-by-16 counter and not to the
“write to SBUF” signal.
For a receive operation, the data bits come in from the
right as 1’s shift out on the left. As soon as the start bit
arrives at the leftmost position in the shift register, (9bit register), it tells the RX control block to perform one
last shift operation: to set RI and to load SBUF and
RB8. The signal to load SBUF and RB8, and to set RI,
will be generated if, and only if, the following conditions
are met at the time the final shift pulse is generated:
-
Either SM2 = 0 or the received stop bit = 1
RI = 0
______________________________________________________________________________________________
www.ramtron.com
page 20 of 40
VRS51x540
If both conditions are met, the stop bit goes into RB8,
the 8 data bits go into SBUF, and RI is activated. If one
of these conditions is not met, the received frame is
completely lost. At this time, whether the above
conditions are met or not, the unit goes back to
searching for a one to zero transition in RXD.
Mode 3
Mode 2
Mode 3 is identical to Mode 2 in all respects but one:
the baud rate. Either Timer 1 or Timer 2 generates the
baud rate in Mode 3.
In Mode 3, 11-bits are transmitted through TXD or
received through RXD. The transactions are
composed of: a Start bit (Low), 8 data bits (LSB first),
a programmable 9th data bit, and one Stop bit (High).
In Mode 2 a total of 11-bits are transmitted through
TXD or received through RXD. The transactions are
composed of: a Start bit (Low), 8 data bits (LSB first), a
programmable 9th data bit, and one Stop bit (High).
FIGURE 20: SERIAL PORT MODE 3 BLOCK DIAGRAM
Internal Bus
1
For transmission, the 9th data bit comes from the TB8
bit of SCON. For example, the parity bit P in the PSW
could be moved into TB8.
Write to
SBUF
Timer 1
Overflow
Q
S
SBUF
TXD
D
th
CLK
In the case of receive, the 9 data bit is automatically
written into RB8 of the SCON register.
Timer 2
Overflow
÷2
ZERO DETECTOR
0 1
SMOD
In Mode 2, the baud rate is programmable to either
1/32 or 1/64 the oscillator frequency.
0
Start
1
Shift
÷16
0
Data
TX Control Unit
TCLK
TX Clock
Send
TI
1
RCLK
÷16
Serial Port
Interrupt
FIGURE 19: SERIAL PORT MODE 2 BLOCK DIAGRAM
SAMPLE
RX Clock
1-0 Transition
Detector
Start
RI
Load
SBUF
RX Control Unit
SHIFT
Internal Bus
1
Write to
SBUF
RXD
Bit
Detector
9-Bit Shift Register
Shift
LOAD SBUF
Q
S
Fosc/2
SBUF
TXD
D
SBUF
CLK
READ SBUF
ZERO DETECTOR
÷2
Internal Bus
0 1
Shift
Stop
Start
SMOD
÷16
TX Clock
Send
TI
÷16
Sample
1-0 Transition
Detector
RXD
Data
TX Control Unit
Serial Port
Interrupt
RX Clock
Control
Start
Bit
Detector
RI
Load
SBUF
RX Control Unit
SHIFT
9-Bit Shift Register
Shift
LOAD SBUF
SBUF
READ SBUF
Internal Bus
______________________________________________________________________________________________
www.ramtron.com
page 21 of 40
VRS51x540
Mode 2 and 3: Additional Information
Reception in Mode 2 and Mode 3
As mentioned earlier, for an operation in these modes,
11 bits are transmitted through TXD or received
through RXD. The signal comprises: a logical low Start
bit, 8 data bits (LSB first), a programmable 9th data bit
and one logical high Stop bit.
One to zero transitions at RXD initiate reception. It is
for this reason that RXD is sampled at a rate of 16
multiplied by the baud rate that has been established.
When a transition is detected, the 1FFh is written into
the input shift register and the divide-by-16 counter is
immediately reset.
On transmit, (TB8 in SCON) can be assigned the value
of 0 or 1. On receive; the 9th data bit goes into RB8 in
SCON. The baud rate is programmable to either 1/32
or 1/64 with the oscillator frequency in Mode 2. Mode
3 may have a variable baud rate generated from either
Timer 1 or Timer 2 depending on the states of TCLK
and RCLK.
Transmission in Mode 2 and Mode 3
The transmission is initiated by any instruction that
makes use of SBUF as the destination register. The 9th
bit position of the transmit shift register is loaded by the
“write to SBUF” signal. This event also informs the TX
control unit that a transmission has been requested.
After the next rollover in the divide-by-16 counter, a
transmission actually begins at T1 of the machine
cycle. It follows the bit times that are synchronized to
the divide-by-16 counter and not to the “write to SBUF”
signal, as in the previous mode.
Transmission begins when the SEND signal is
activated, which places the Start bit at TXD. Data is
activated one bit time later. This activation enables the
output bit of the transmit shift register to TXD. The first
shift pulse occurs one bit time after that.
The first shift clocks a Stop bit (1) into the 9th bit
position of the shift register to TXD. Thereafter, only
zeros are clocked in. Thus, as data bits shift out to the
right, zeros are clocked in from the left. When TB8 is at
the output position of the shift register, the stop bit is
just to the left of TB8, and all positions to the left of that
contain zeros. This condition signals to the TX control
unit to shift one more time and set TI, while deactivating SEND. This occurs at the 11th divide-by-16
rollover after “write to SBUF”.
During the 7th, 8th and 9th counter states of each bit
time; the bit detector samples the value of RXD. The
accepted value is the value that was seen in at least
two of the three samples. If the value accepted during
the first bit time is not zero, the receive circuits are
reset and the unit goes back to searching for another
one to zero transition. If the start bit is valid, it is shifted
into the input shift register, and the reception of the rest
of the frame will proceed.
For a receive operation, the data bits come in from the
right as 1’s shift out on the left. As soon as the start bit
arrives at the leftmost position in the shift register (9-bit
register), it tells the RX control block to do one more
shift, to set RI, and to load SBUF and RB8. The signal
to set RI and to load SBUF and RB8 will be generated
if, and only if, the following conditions are satisfied at
the instance when the final shift pulse is generated:
- Either SM2 = 0 or the received 9th bit is equal to 1
- RI = 0
If both conditions are met, the 9th data bit received
goes into RB8, and the first 8 data bits go into SBUF. If
one of these conditions is not met, the received frame
is completely lost. One bit time later, whether the
above conditions are met or not, the unit goes back to
searching for a one to zero transition at the RXD input.
Please note that the value of the received stop bit is
unrelated to SBUF, RB8 or RI.
______________________________________________________________________________________________
www.ramtron.com
page 22 of 40
VRS51x540
UART Baud Rate Calculation
The value to write into the TH1 register is defined by
the following formula:
In Mode 0, the baud rate is fixed and can be
represented by the following formula:
TH1 = 256 Mode 0 Baud Rate = Oscillator Frequency
12
In Mode 2, the baud rate depends on the value of the
SMOD bit in the PCON SFR. From the formula below,
we can see that if SMOD = 0 (which is the value on
reset), the baud rate is 1/32 the oscillator frequency.
2SMODx Fosc
32 x 12x (Baud Rate)
It is possible to use Timer 1 in 16-bit mode to generate
the baud rate for the serial port. To do this, leave the
Timer 1 interrupt enabled, configure the timer to run as
a 16-bit timer (high nibble of TMOD = 0001B), and use
the Timer 1 interrupt to perform a 16-bit software
reload. This can achieve very low baud rates.
Generating Baud Rates with Timer 2
Mode 2 Baud Rate = 2SMOD x (Oscillator Frequency)
64
The Timer 1 and/or Timer 2 overflow rate determines
the baud rates in modes 1 and 3.
Timer 2 is often preferred to generate the baud rate, as
it can be easily configured to operate as a 16-bit timer
with auto-reload. This allows for much better resolution
than using Timer 1 in 8-bit auto-reload mode.
The baud rate using Timer 2 is defined as:
Generating Baud Rates with Timer 1
When Timer 1 functions as a baud rate generator, the
baud rate in modes 1 and 3 are determined by the
Timer 1 overflow rate.
SMOD
Mode 1, 3 Baud Rate = 2
x Timer 1 Overflow Rate
32
Timer 1 must be configured as an 8-bit timer (TL1) with
auto-reload with TH1 value when an overflow occurs
(Mode 2). In this application, the Timer 1 interrupt
should be disabled.
The two following formulas can be used to calculate
the baud rate and the reload value to written into the
TH1 register.
Mode 1, 3 Baud Rate =
Mode 1, 3 Baud Rate = Timer 2 Overflow Rate
16
The timer can be configured as either a timer or a
counter in any of its 3 running modes. In most
applications, it is configured as a timer (C/T2 is set to
0).
To make the Timer 2 operate as a baud rate generator
the TCLK and RCLK bits of the T2CON register must
be set to 1.
The baud rate generator mode is similar to the autoreload mode in that an overflow in TH2 causes the
Timer 2 registers to be reloaded with the 16-bit value in
registers RCAP2H and RCAP2L, which are preset by
software. However, when Timer 2 is configured as a
baud rate generator, its clock source is Osc/2.
SMOD
2
x Fosc
32 x 12(256 – TH1)
______________________________________________________________________________________________
www.ramtron.com
page 23 of 40
VRS51x540
The following formula can be used to calculate the
baud rate in modes 1 and 3 using the Timer 2:
Modes 1, 3 Baud Rate =
Oscillator Frequency
32x[65536 – (RCAP2H, RCAP2L)]
The formula below is used to define the reload value to
put into the RCAP2h, RCAP2L registers to achieve a
given baud rate.
(RCAP2H, RCAP2L) = 65536 -
Fosc
32x[Baud Rate]
In the above formula, RCAP2H and RCAP2L are the
contents of RCAP2H and RCAP2L taken as a 16-bit
unsigned integer.
Note that a rollover in TH2 does not set TF2, and will
not generate an interrupt and because of this, the
Timer 2 interrupt does not have to be disabled when
Timer 2 is configured in baud rate generator mode.
Also, if EXEN2 is set, a 1-to-0 transition in T2EX will
set EXF2 but will not cause a reload from RCAP2x to
Tx2. Therefore, when Timer 2 is used as a baud rate
generator, T2EX can be used as an extra external
interrupt.
Furthermore, when Timer 2 is running (TR2 is set to 1)
as a timer in baud rate generator mode, the user
should not try to read or write to TH2 or TL2. When
operating under these conditions, the timer is being
incremented every state time and the results of a read
or write command may be inaccurate.
The RCAP2 registers, however, may be read but
should not be written to, because a write may overlap a
reload operation and generate write and/or reload
errors. In this case, before accessing the Timer 2 or
RCAP2 registers, be sure to turn the timer off by
clearing TR2.
______________________________________________________________________________________________
www.ramtron.com
page 24 of 40
VRS51x540
Interrupts
Interrupt Vectors
The VRS51x540 has 8 interrupts and 7 interrupt
vectors (including reset) used for handling.
The table below specifies each interrupt source, its flag
and its vector address.
The interrupt can be enabled via the IE register shown
below:
T ABLE 20: INTERRUPT VECTOR CORRESPONDING FLAGS ANS VECTOR ADDRESS
Interrupt Source
Flag
T ABLE 19: IEN0 INTERRUPT E NABLE REGISTER –SFR A8H
7
6
5
4
3
EA
-
ET2
ES
ET1
Bit
7
Mnemonic
EA
6
-
5
4
3
2
1
0
ET2
ES
ET1
EX1
ET0
EX0
2
EX1
1
0
ET0
EX0
Description
Disables All Interrupts
0: no interrupt acknowledgment
1: Each interrupt source is individually
enabled or disabled by setting or clearing
its enable bit.
Reserved
Timer 2 Interrupt Enable Bit
Serial Port Interrupt Enable Bit
Timer 1 Interrupt Enable Bit
External Interrupt 1 Enable Bit
Timer 0 Interrupt Enable Bit
External Interrupt 0 Enable Bit
The following figure illustrates the various interrupt
sources on the VRS51x540.
FIGURE 21: INTERRUPT SOURCES
INT0
IT0
WDRESET
IE0
TF0
IE1
TF1
RI+TI
TF2+EXF2
External Interrupts
The VRS51x540 has two external interrupt inputs
named INT0 and INT1. These interrupt lines are
shared with P3.2 and P3.3.
The bits IT0 and IT1 of the TCON register determine
whether the external interrupts are level or edge
sensitive.
If ITx = 1, the interrupt will be raised when a 1 to 0
transition occurs at the interrupt pin. For the interrupt
to be noticed by the processor, the duration of the sum
high and low condition must be at least equal to 12
oscillator cycles.
IE0
If ITx = 0, the interrupt will occur when a logic low
condition is present on the interrupt pin.
TF0
INT1
RESET (+ WDT)
INT0
Timer 0
INT1
Timer 1
Serial Port
Timer 2
Vector
Address
0000h
0003h
000Bh
0013h
001Bh
0023h
002Bh
IT1
IE1
INTERRUPT
SOURCES
The state of the external interrupt, when enabled, can
be monitored using the flags, IE0 and IE1 of the TCON
register that are set when the interrupt condition
occurs.
TF1
T1
RI
TF2
EXF2
In the case where the interrupt was configured as edge
sensitive, the associated flag is automatically cleared
when the interrupt is serviced.
If the interrupt is configured as level sensitive, then the
interrupt flag must be cleared by the software.
______________________________________________________________________________________________
www.ramtron.com
page 25 of 40
VRS51x540
Timer 0 and Timer 1 Interrupt
Execution of an Interrupt
Both Timer 0 and Timer 1 can be configured to
generate an interrupt when a rollover of the
timer/counter occurs (except Timer 0 in Mode 3).
When the processor receives an interrupt request, an
automatic jump to the desired subroutine occurs. This
jump is similar to executing a branch to a subroutine
instruction: the processor automatically saves the
address of the next instruction on the stack. An internal
flag is set to indicate that an interrupt is taking place,
and then the jump instruction is executed. An interrupt
subroutine must always end with the RETI instruction.
This instruction allows users to retrieve the return
address placed on the stack.
The TF0 and TF1 flags serve to monitor timer overflow
occurring from Timer 0 and Timer 1. These interrupt
flags are automatically cleared when the interrupt is
serviced.
Timer 2 Interrupt
A Timer 2 interrupt can occur if TF2 and/or EXF2 flags
are set to 1 and if the Timer 2 interrupt is enabled.
The RETI instruction also allows updating of the
internal flag that will take into account an interrupt with
the same priority.
The TF2 flag is set when a rollover of the Timer 2
Counter/Timer occurs. The EXF2 flag can be set by a 1
to 0 transition on the T2EX pin by the software.
Interrupt Enable and Interrupt Priority
Note that neither flag is cleared by the hardware upon
execution of the interrupt service routine. The service
routine may have to determine whether it was TF2 or
EXF2 that generated the interrupt. These flag bits will
have to be cleared by the software.
When the VRS51x540 is initialized, all interrupt
sources are inhibited by the bits of the IE register being
reset to 0. It is necessary to start by enabling the
interrupt sources that the application requires. This is
achieved by setting bits in the IE register, as discussed
previously.
Every bit that generates interrupts can either be
cleared or set by the software, yielding the same result
as when the operation is done by the hardware. In
other words, pending interrupts can be cancelled and
interrupts can be generated by the software.
This register is part of the bit addressable internal
RAM. For this reason, it is possible to modify each bit
individually in one instruction without having to modify
the other bits of the register. All interrupts can be
inhibited by setting EA to 0.
Serial Port Interrupt
The order in which interrupts are serviced is shown in
the following table:
The serial port can generate an interrupt upon byte
reception or once the byte transmission is completed.
Those two conditions share the same interrupt vector
and it is up to the user developed interrupt service
routine software to ascertain the cause of the interrupt
by looking at the serial interrupt flags RI and TI.
Note that neither of these flags is cleared by the
hardware upon execution of the interrupt service
routine. The software must clear these flags.
T ABLE 21: INTERRUPT NATURAL PRIORITY
Interrupt Source
RESET + WDT (Highest Priority)
IE0
TF0
IE1
TF1
RI+TI
TF2+EXF2 (Lowest Priority)
______________________________________________________________________________________________
www.ramtron.com
page 26 of 40
VRS51x540
Modifying the Interrupt Order of Priority
The VRS51x540 allows the user to modify the natural
priority of the interrupts by programming the bits in the
IP (Interrupt Priority) register. When any bit in this
register is set to 1, it gives the corresponding source a
greater priority than interrupts coming from sources
that don’t have their corresponding IP bit set to 1.
The IP register is represented in the table below.
T ABLE 22: IP INTERRUPT PRIORITY REGISTER –SFR B8H
7
6
5
4
3
EA
-
ET2
ES
ET1
2
EX1
1
0
ET0
EX0
Bit
7
6
Mnemonic
-
Description
5
4
3
2
1
0
PT2
PS
PT1
PX1
PT0
PX0
Gives Timer 2 Interrupt Higher Priority
Gives Serial Port Interrupt Higher Priority
Gives Timer 1 Interrupt Higher Priority
Gives INT1 Interrupt Higher Priority
Gives Timer 0 Interrupt Higher Priority
Gives INT0 Interrupt Higher Priority
The user should check the WDRESET bit of the
SYSCON register whenever an unpredicted reset has
taken place.
The WDT timeout delay can be adjusted by configuring
the clock divider input for the time base source clock of
the WDT. To select the divider value, bit2-bit0
(WDPS2~WDPS0) of the Watchdog Timer Control
Register (WDTCON) should be set accordingly.
Clearing the WDT is accomplished by setting the CLR
bit of the WDTCON to 1. This action will clear the
contents of the 16-bit counter and force it to restart.
Watchdog Timer Registers
Two registers of the VRS51x540 devices are
associated with the Watchdog Timer: WDTCON and
the SYSCON registers. The WDTCON register allows
the user to enable the WDT, to clear the counter and to
divide the clock source. The WDRESET bit of the
SYSCON register indicates whether the Watchdog
Timer has caused the device reset.
T ABLE 23: WATCHDOG T IMER REGISTERS: WDTCON – SFR 9FH
Watchdog Timer
The Watchdog Timer (WDT) is a 16-bit free-running
counter that generates a reset signal if the counter
overflows. The WDT is useful for systems that are
susceptible to noise, power glitches and other
conditions that can cause the software to go into
infinite dead loops or runaways. The WDT function
gives the user software a recovery mechanism from
abnormal software operation.
7
WDTE
Bit
7
6
5
[4:3]
2
1
0
6
Unused
5
WDCLR
4
3
Unused
2
1
0
WDTPS [2:0]
Mnemonic
WDTE
Unused
WDCLR
Unused
Description
Watchdog Timer Enable Bit
Watchdog Timer Counter Clear Bit
-
WDPS [2:0]
Watchdog Timer Clock Source Divider
The Watchdog Timer of the VRS51x540 is driven by
the device’s oscillator.
To enable the WDT, the user must set bit 7 (WDTE) of
the WDTCON register to 1. Once WDTE has been set
to 1, the 16-bit counter will start to count with the
selected time base source clock configured in
WDPS2~WDPS0. The Watchdog Timer will generate a
reset signal if an overflow has taken place.
The WDTE bit will be cleared to 0 automatically when
the device is reset by either the hardware or a WDT
reset.
Once the WDT is enabled, the user software must
clear it periodically. In the case where the WDT is not
cleared, its overflow will trigger a reset of the device.
______________________________________________________________________________________________
www.ramtron.com
page 27 of 40
VRS51x540
The table below shows example Watchdog timeout
periods that the user will obtain for different values of
the WDPSx bits of the Watchdog Timer Register.
T ABLE 24: WATCHDOG T IMER PERIOD VS. WDWDPS [2:0] BIT
Fosc
Division factor
WDT Timeout (ms)
Fosc = 20MHz
000
8
26.2
001
16
52.4
010
011
32
64
104.8
209.7
100
128
419.4
101
256
110
512
1024
838.9
1677.7
WDPS [2:0]
111
XTAL
C1
C2
R
T ABLE 25: T HE SYSTEM CONTROL REGISTER (SYSCON)–SFR BFH
5
WDRESET
Bit
7
[6:3]
2
1
0
Mnemonic
WDRESET
Unused
Unused
Unused
ALEI
4
Unused
3
2
1
XRAME
3MHz
30 pF
30 pF
open
6MHz
30 pF
30 pF
open
12MHz
30 pF
30 pF
open
16MHz
30 pF
30 pF
open
25MHz
15 pF
15 pF
62KO
Note: Oscillator circuits may differ with different
crystals or ceramic resonators in higher oscillation
frequency.
3355.4
The System Control register is used to monitor the
status of the Watchdog Timer and inhibit the address
Latch Enable signal output.
6
The crystal connected to the VRS51x540 oscillator
input should be of a parallel type, operating in
fundamental mode.
The following table shows the value of capacitors and
feedback resistor that must be used at different
operating frequencies.
The System Control Register
7
Crystal Consideration
0
ALEI
Description
Watchdog Timer Reset Status Bit
-
Crystals or ceramic resonator characteristics vary from
one manufacturer to the other.
The user should check the specific crystal or ceramic
resonator technical literature available or contact the
manufacturer to select the appropriate values for the
external components.
XTAL1
1: Enable Electromagnetic Interference
Reducer
0: Disable Electromagnetic Interference
Reducer
The WDRESET bit of the SYSCON register is the
Watchdog Timer Reset bit. It will be set to 1 when a
reset signal is generated by the WDT overflow. The
user should check the WDRESET bit state if a reset
has taken place in application where the Watchdog
timer is activated
XTAL
VRS51x540
R
XTAL2
C1
C2
Reduced EMI Function
The VRS51x540 can also be set up to reduce its EMI
(electromagnetic interference) by setting bit 0 (ALEI) of
the SYSCON register to 1. This function will inhibit the
Fosc/6Hz clock signal output to the ALE pin.
______________________________________________________________________________________________
www.ramtron.com
page 28 of 40
VRS51x540
Operating Conditions
T ABLE 26: OPERATING CONDITIONS
Symbol
TA
TS
VCC5V
VCC3V
Fosc 25
Description
Operating temperature
Storage temperature
Supply voltage
Supply voltage
Oscillator Frequency
Min.
-40
-55
4.5
3.0
3.0
Typ.
25
25
5.0
3.3
25
Max.
85
155
5.5
3.6
25
Unit
ºC
ºC
V
V
MHz
Remarks
Ambient temperature operating
5 Volts devices
3.3 Volts devices
For 5V & 3.3V application
DC Characteristics
T ABLE 27: DC CHARACTERISTICS
AMBIENT T EMPERATURE = -40°C TO 85°C, 3.0V TO 5.5V
Symbol
VIL1
VIL2
VIH1
VI H2
VOL1
VOL2
Parameter
Input Low Voltage
Input Low Voltage
Input High Voltage
Input High Voltage
Output Low Voltage
Output Low Voltage
Valid
P o r t 0,1,2,3,4,#EA
RES, XTAL1
P o r t 0,1,2,3,4,#EA
RES, XTAL1
Port 0, ALE, #PSEN
P o r t 1,2,3,4
VOH1
Output High Voltage
Port 0
VOH2
Output High Voltage
Port
1,2,3,4,ALE,#PSEN
IIL
Logical 0 Input Current
ITL
ILI
R RES
Logical Transition
Current
Input Leakage Current
Reset Pull-down
Resistance
C -10
Pin Capacitance
IC C
Power Supply Current
Max.
0.8
0.8
VCC+0.5
VCC+0.5
0.45
0.45
Unit
V
V
V
V
V
V
V
V
V
V
Test Conditions
P o r t 1,2,3,4
-75
uA
Vin=0.45V
P o r t 1,2,3,4
-650
uA
Vin=2.OV
P o r t 0, #EA
+10
uA
0.45V<Vin<VCC
300
Kohm
10
pF
Freq=1 MHz, Ta=25°C
20
6.5
150
mA
mA
uA
Active mode 12MHz
Idle mode, 12MHz
Power down mode
RES
Min.
-0.5
0
2.0
70% VCC
2.4
90% VCC
2.4
90% VCC
50
VDD
FIGURE 22: ICC IDLE MODE T EST CIRCUIT
IOL=3.2mA
IOL=1.6mA
IOH=-800uA (Vcc = 5V)
IOH=-80uA
IOH=-60uA (Vcc = 5V)
IOH=-10uA
FIGURE 23: ICC ACTIVE MODE T EST CIRCUIT
Vcc
Vcc
Vcc
Icc
RST
VCC
PO
EA
Icc
VCC
8
RST
VRS51x540
PO
EA
8
VRS51x540
(NC)
XTAL2
Clock Signal
(NC)
XTAL1
VSS
Clock Signal
XTAL2
XTAL1
VSS
______________________________________________________________________________________________
www.ramtron.com
page 29 of 40
VRS51x540
AC Characteristics
T ABLE 28: AC CHARACTERISTICS
Symbol
T LHLL
T AVLL
T LLAX
T LLIV
T LLPL
T PLPH
T PLIV
T PXIX
T PXIZ
T AVI V
T PLAZ
T RLRH
T WLWH
T RLDV
T RHDX
T RHDZ
T LLDV
T AVDV
T LLYL
T AVYL
T QVWH
T QVWX
T WHQX
T RLAZ
T YALH
T CHCL
T CLCX
T CLCH
T CHCX
T , T C LCL
Parameter
ALE Pulse Width
Address Valid to ALE Low
Address Hold after ALE Low
ALE Low to Valid Instruction In
ALE Low to #PSEN low
#PSEN Pulse Width
#PSEN Low to Valid Instruction In
Instruction Hold after #PSEN
Instruction Float after #PSEN
Address to Valid Instruction In
#PSEN Low to Address Float
#RD Pulse Width
#WR Pulse Width
#RD Low to Valid Data In
Data Hold after #RD
Data Float after #RD
ALE Low to Valid Data In
Address to Valid Data In
ALE low to #WR High or #RD Low
Address Valid to #WR or #RD Low
Data Valid to #WR High
Data Valid to #WR Transition
Data Hold after #WR
#RD Low to Address Float
#W R or #RD High to ALE High
Clock Fall Time
Clock Low Time
Clock Rise Time
Clock High Time
Clock Period
Valid
Cycle
RD/WRT
RD/WRT
RD/WRT
RD
RD
RD
RD
RD
RD
RD
RD
RD
WRT
RD
RD
RD
RD
RD
RD/WRT
RD/WRT
WRT
WRT
WRT
RD
RD/WRT
Fosc 16
Min.
115
43
53
Type
Max.
Variable Fosc
Min.
2xT - 10
T - 20
T - 10
Type
240
53
173
4xT - 10
T - 10
3xT - 15
177
0
3xT -10
0
87
292
10
365
365
T + 25
5xT - 20
10
6xT - 10
6xT - 10
302
0
178
230
403
38
73
53
63
Max.
5xT - 10
0
145
590
542
197
72
2xT + 20
8xT - 10
9xT - 20
3xT + 10
3xT - 10
4xT - 20
7xT - 35
T - 25
T + 10
5
T+10
T -10
1/fosc
Unit
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
______________________________________________________________________________________________
www.ramtron.com
page 30 of 40
VRS51x540
Data Memory Read Cycle Timing
The following timing diagram shows what occurs at each signal during a Data Memory Read Cycle.
FIGURE 24: DATA MEMORY READ CYCLE T IMING
T12
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
T1
T2
T3
OSC
1
ALE
2
#PSEN
5
#RD
7
3
ADDRESS A15-A8
PORT2
3
PORT0
INST in
Float
A7-A0
4
6
Float
8
Data in
Float
ADDRESS or
Float
______________________________________________________________________________________________
www.ramtron.com
page 31 of 40
VRS51x540
Program Memory Read Cycle Timing
The following timing diagram shows what occurs at each signal during a Program Memory Read Cycle.
FIGURE 25: PROGRAM MEMORY READ CYCLE
T12
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
T1
T2
T3
OSC
ALE
1
2
5
#PSEN
7
#RD,#WR
3
ADDRESS A15-A8
PORT2
PORT0
Float
3
4
6
A7-A0 Float
INST in
ADDRESS A15-A8
8
Float
A7-A0
Float
INST in
Float
______________________________________________________________________________________________
www.ramtron.com
page 32 of 40
VRS51x540
Data Memory Write Cycle Timing
The following timing diagram shows what occurs at each signal during a Data Memory Write Cycle.
FIGURE 26: DATA MEMORY WRITE CYCLE T IMING
T12
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
T1
T2
T3
OSC
ALE
1
#PSEN
5
#WR
6
2
ADDRESS A15-A8
PORT2
2
PORT0
INST in
Float
A7-A0
3
4
Data out
ADDRESS or
Float
______________________________________________________________________________________________
www.ramtron.com
page 33 of 40
VRS51x540
I/O Port Timing
The following timing diagram shows what occurs during I/O Port Timing.
FIGURE 27: I/O PORTS T IMING
T7
T8
T9
T10
T11
T12
T1
T2
T3
T4
T5
T6
T7
T8
X1
Sampled
Inputs P0,P1
Sampled
Inputs P2,P3
Output by Mov
Px, Src
RxD at Serial
Port Shift
Clock Mode 0
Current Data
Next Data
Sampled
______________________________________________________________________________________________
www.ramtron.com
page 34 of 40
VRS51x540
External Clock Timing
FIGURE 28: T IMING REQUIREMENT OF EXTERNAL CLOCK (VSS= 0.0V IS ASSUMED)
TCLCL
Vdd - 0.5V
0.45V
70% Vdd
20% Vdd-0.1V
TCLCX
TCHCX
TCHCL
TCLCH
External Program Memory Read Cycle
The following timing diagram shows what occurs at each signal during an External Program Memory Read Cycle.
FIGURE 29: EXTERNAL PROGRAM MEMORY READ CYCLE
TPLPH
#PSEN
TLLPL
ALE
TLHLL
TPXIZ
TAVLL
PORT 0
TLLAX
A0-A7
TPLIV
TPLAZ
TPXIX
Instruction IN
A0-A7
TAVIV
PORT2
P2.0-P2.7 or AB-A15 from DPH
A8-A15
______________________________________________________________________________________________
www.ramtron.com
page 35 of 40
VRS51x540
External Data Memory Read Cycle
The following timing diagram shows what occurs at each signal during an External Data Memory Read Cycle.
FIGURE 30: EXTERNAL DATA MEMORY READ CYCLE
#PSEN
TYHLH
ALE
TLLDV
TRLRH
TLLYL
#RD
TAVLL
PORT 0
TRLDV
TLLAX
TRLAZ
A0-A7
From Ri or DPL
TRHDZ
TRHDX
DATA IN
A0-A7
From PCL
INSTRL
IN
TAVYL
TAVDV
PORT 2
P2.0-P2.7 or A8 -A15 from DPH
A8-A15 from PCH
______________________________________________________________________________________________
www.ramtron.com
page 36 of 40
VRS51x540
External Data Memory Write Cycle
The following timing diagram shows what occurs at each signal during an External Data Memory Write Cycle.
FIGURE 31: EXTERNAL DATA MEMORY WRITE CYCLE
#PSEN
TYHLH
ALE
TLHLL
TLLYL
TWLWH
#WR
TAVLL
TQVWX
TWHQX
TLLAX
TQVWH
PORT 0
A0-A7
From Ri or DPL
DATA OUT
A0-A7
From PCL
INSTRL
IN
TAVYL
PORT 2
P2.0-P2.7 or A8-A15 from DPH
A8-A15 from PCH
.
______________________________________________________________________________________________
www.ramtron.com
page 37 of 40
VRS51x540
Plastic Chip Carrier (PLCC-44)
L
VRS51x540
PLCC-44
GE
E
HE
Y
A2
D
A1
A
HD
TABLE 29: DIMENSIONS OF PLCC-44 CHIP CARRIER
C
e
b1
b
GD
Note:
1. Dimensions D & E do not include interlead Flash.
2. Dimension B1 does not include dambar
protrusion/intrusion.
3. Controlling dimension: Inch
4. General appearance spec should be based on
final visual inspection spec.
Symbol
A
Al
A2
bl
b
C
D
E
e
GD
GE
HD
HE
L
?
?y
Dimension in inch
Minimal/Maximal
-/0.185
0.020/0.145/0.155
0.026/0.032
0.016/0.022
0.008/0.014
0.648/0.658
0.648/0.658
0.050 BSC
0.590/0.630
0.590/0.630
0.680/0.700
0.680/0.700
0.090/0.110
-/0.004
/
Dimension in mm
Minimal/Maximal
-/4.70
0.51/
3.68/3.94
0.66/0.81
0.41/0.56
0.20/0.36
16.46/16.71
16.46/16.71
1.27 BSC
14.99/16.00
14.99/16.00
17.27/17.78
17.27/17.78
2.29/2.79
-/0.10
/
______________________________________________________________________________________________
www.ramtron.com
page 38 of 40
VRS51x540
C
Quad Flat Package (QFP)
L
L1
S
S
VRS51x540
QFP-44
D2 D1 D
b
2
R1
A2
A1
Gage Plane
0.25mm
A
3
R2
E2
E1
E
T ABLE 30: DIMENSIONS OF QFP-44 CHIP CARRIER
Symbol
e1
Seating Plane
e
Note:
1. Dimensions D1 and E1 do not include mold
protrusion.
2. Allowance protrusion is 0.25mm per side.
3. Dimensions D1 and E1 do not include mold
mismatch and are determined datum plane.
4. Dimension b does not include dambar
protrusion.
5. Allowance dambar protrusion shall be 0.08 mm
total in excess of the b dimension at maximum
material condition. Dambar cannot be located
on the lower radius of the lead foot.
C
A
Al
A2
b
c
D
D1
D2
E
E1
E2
e
L
L1
R1
R2
S
0
?1
?2
?3
?C
Dimension in in.
Minimal/Maximal
-/0.100
0.006/0.014
0.071 / 0.087
0.012/0.018
0.004 / 0.009
0.520 BSC
0.394 BSC
0.315
0.520 BSC
0.394 BSC
0.315
0.031 BSC
0.029 / 0.041
0.063
0.005/0.005/0.012
0.008/0°/7°
0°/ 10° REF
7° REF
0.004
Dimension in mm
Minimal/Maximal
-/2.55
0.15/0.35
1.80/2.20
0.30/0.45
0.09/0.20
13.20 BSC
10.00 BSC
8.00
13.20 BSC
10.00 BSC
8.00
0.80 BSC
0.73/1.03
1.60
0.13/0.13/0.30
0.20/as left
as left
as left
as left
0.10
______________________________________________________________________________________________
www.ramtron.com
page 39 of 40
VRS51x540
Ordering Information
Device Number Structure
VRS51x540 Ordering Options
Device Number
VRS51C540-40-L
VRS51L540-25-L
VRS51C540-40-Q
VRS51L540-25-Q
VRS51C540-40-P
VRS51L540-25-P
VRS51C540-40-LG
VRS51L540-25-LG
VRS51C540-40-QG
VRS51L540-25-QG
VRS51C540-40-PG
VRS51L540-25-PG
Flash Size
RAM Size
4KB
4KB
4KB
4KB
4KB
4KB
4KB
4KB
4KB
4KB
4KB
4KB
128 Bytes
128 Bytes
128 Bytes
128 Bytes
128 Bytes
128 Bytes
128 Bytes
128 Bytes
128 Bytes
128 Bytes
128 Bytes
128 Bytes
Package
Option
PLCC-44
PLCC-44
QFP-44
QFP-44
DIP-40
DIP-40
PLCC-44
PLCC-44
QFP-44
QFP-44
DIP-40
DIP-40
Voltage
Temperature
Frequency
4.5V to 5.5V
3.0V to 3.6V
4.5V to 5.5V
3.0V to 3.6V
4.5V to 5.5V
3.0V to 3.6V
4.5V to 5.5V
3.0V to 3.6V
4.5V to 5.5V
3.0V to 3.6V
4.5V to 5.5V
3.0V to 3.6V
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
40MHz
25MHz
40MHz
25MHz
40MHz
25MHz
40MHz
25MHz
40MHz
25MHz
40MHz
25MHz
Disclaimers
Right to make change - Ramtron reserves the right to make changes to its products - including circuitry, software and services - without notice at
any time. Customers should obtain the most current and relevant information before placing orders.
Use in applications - Ramtron assumes no responsibility or liability for the use of any of its products, and conveys no license or title under any
patent, copyright or mask work right to these products and makes no representations or warranties that these products are free from patent,
copyright or mask work right infringement unless otherwise specified. Customers are responsible for product design and applications using Ramtron
parts. Ramtron assumes no liability for applications assistance or customer product design.
Life support – Ramtron products are not designed for use in life support systems or devices. Ramtron customers using or selling Ramtron products
for use in such applications do so at their own risk and agree to fully indemnify Ramtron for any damages resulting from such applications.
______________________________________________________________________________________________
www.ramtron.com
page 40 of 40