TI TL16C752CIRHBR

TL16C752C
DUAL UART
WITH 64-BYTE FIFO
www.ti.com
SLLS646 – MARCH 2008
FEATURES
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ST16C654/654D Pin Compatible With
Additional Enhancements (PFB Package Only)
Supports up to 24-MHz Crystal Input Clock
(1.5 Mbps)
Supports up to 48-MHz Oscillator Input Clock
(3 Mbps) for 5-V Operation
Supports up to 32-MHz Oscillator Input Clock
(2 Mbps) for 3.3-V Operation
Supports up to 24-MHz Input Clock (1.5 Mbps)
for 2.5-V Operation
Supports up to 16-MHz Input Clock (1 Mbps)
for 1.8-V Operation
64-Byte Transmit FIFO
64-Byte Receive FIFO With Error Flags
Programmable and Selectable Transmit and
Receive FIFO Trigger Levels for DMA and
Interrupt Generation
Programmable Receive FIFO Trigger Levels for
Software/Hardware Flow Control
Software/Hardware Flow Control
– Programmable Xon/Xoff Characters
– Programmable Auto-RTS and Auto-CTS
Optional Data Flow Resume by Xon Any
Character
DMA Signaling Capability for Both Received
and Transmitted Data on PN Package
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RS-485 Mode Support
Support 1.8-V, 2.5-V, 3.3-V, or 5-V Supply
Characterized for Operation From –40°C to
85°C, Available in Commercial and Industrial
Temperature Grades
Software-Selectable Baud-Rate Generator
Prescalable Provides Additional Divide-by-4
Function
Programmable Sleep Mode
Programmable Serial Interface Characteristics
– 5-, 6-, 7-, or 8-Bit Characters
– Even, Odd, or No Parity Bit Generation and
Detection
– 1-, 1.5-, or 2-Stop Bit Generation
False Start Bit Detection
Complete Status Reporting Capabilities in
Both Normal and Sleep Mode
Line Break Generation and Detection
Internal Test and Loopback Capabilities
Fully Prioritized Interrupt System Controls
Modem Control Functions (CTS, RTS, DSR,
DTR, RI, and CD)
IrDA Capability
DESCRIPTION
The TL16C752C is a quad universal asynchronous receiver/transmitter (UART) with 64-byte FIFOs, automatic
hardware/software flow control, and data rates up to 3 Mbps. It incorporates the functionality of four UARTs, each
UART having its own register set and FIFOs. The four UARTs share only the data bus interface and clock
source, otherwise they operate independently. Another name for the UART function is asynchronous
communications element (ACE), and these terms are used interchangeably. The bulk of this document describes
the behavior of each ACE, with the understanding that four such devices are incorporated into the TL16C752C.
The TL16C752C offers enhanced features. It has a transmission control register (TCR) that stores received FIFO
threshold level to start/stop transmission during hardware and software flow control. With the FIFO RDY register,
the software gets the status of TXRDY/RXRDY for all four ports in one access. On-chip status registers provide
the user with error indications, operational status, and modem interface control. System interrupts may be
tailored to meet user requirements. An internal loopback capability allows onboard diagnostics.
Each UART transmits data sent to it from the peripheral 8-bit bus on the TX signal and receives characters on
the RX signal. Characters can be programmed to be 5, 6, 7, or 8 bits. The UART has a 64-byte receive FIFO and
transmit FIFO and can be programmed to interrupt at different trigger levels. The UART generates its own
desired baud rate based upon a programmable divisor and its input clock. It can transmit even, odd, or no parity
and 1-, 1.5-, or 2-stop bits. The receiver can detect break, idle or framing errors, FIFO overflow, and parity errors.
The transmitter can detect FIFO underflow. The UART also contains a software interface for modem control
operations, and software flow control and hardware flow control capabilities.
The TL16C752C is available in a 32-pin QFN (RHB) package. A 48-pin QFP (PFB) package will be available in
late 2008.
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2008, Texas Instruments Incorporated
TL16C752C
DUAL UART
WITH 64-BYTE FIFO
www.ti.com
SLLS646 – MARCH 2008
D4
D3
D2
D1
D0
TXRDYA
VCC
RA
CDA
DSRA
CTSA
NC
PFB PACKAGE
(TOP VIEW)
48 47 46 45 44 43 42 41
D5
D6
D7
RXB
RXA
TXRDYB
TXA
TXB
OPB
CSA
CSB
NC
39 38 37
1
36
2
35
3
34
4
33
5
32
6
31
TL16C752CPFB
7
RESET
DTRB
DTRA
RTSA
OPA
RXRDYA
INTA
INTB
A0
A1
A2
NC
30
8
29
9
28
10
27
11
26
12
25
CDB
GND
RXRDYB
IOR
DSRB
RIB
RTSB
CTSB
NC
XTAL1
XTAL2
IOW
13 14 15 16 17 18 19 20 21 22 23 24
NC No internal connection
CTSA
25
D1
D0
D2
29
28
VCC
D3
30
26
D4
31
27
D5
32
RHB PACKAGE
(TOP VIEW)
D6
1
RESET
D7
2
23
DTRB
RXB
3
22
DTRA
RXA
4
21
RTSA
TXA
5
20
INTA
TXB
6
19
INTB
CSA
7
18
A0
CSB
8
17
A1
12
13
14
15
16
RTSB
CTSB
A2
11
IOW
IOR
10
XTAL2
GND
9
XTAL1
24
TL16C752CRHB
Note: The 32-pin RHB package does not provide access to DSRA, DSRB, RIA, RIB, CDA, CDB inputs or OPA, OPB,
RXRDYA, RXRDYB, TXRDYA outputs.
2
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DUAL UART
WITH 64-BYTE FIFO
www.ti.com
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TERMINAL FUNCTIONS
TERMINAL
NAME
NO.
I/O
DESCRIPTION
PFB
RHB
A0
28
18
I
Address bit 0 select. Internal registers address selection. Refer to Table 7 for Register
Address Map.
A1
27
17
I
Address bit 1 select. Internal registers address selection. Refer to Table 7 for Register
Address Map.
A2
26
16
I
Address bit 2 select. Internal registers address selection. Refer to Table 7 for Register
Address Map.
I
Carrier detect (active low). These inputs are associated with individual UART channels A
through B. A low on these pins indicates that a carrier has been detected by the modem
for that channel.
I
Chip select A and B (active low). These pins enable data transfers between the user
CPU and the TL16C752C for the channel(s) addressed. Individual UART sections (A, B,
C, D) are addressed by providing a low on the respective CSA through CSD pin.
CDA, CDB,
40, 16
CSA, CSB,
10, 11
7, 8
CTSA, CTSB,
38, 23
25, 15
I
Clear to send (active low). These inputs are associated with individual UART channels A
and B. A low on the CTS pins indicates the modem or data set is ready to accept
transmit data from the TL16C752C. Status can be checked by reading MSR[4]. These
pins only affect the transmit and receive operations when auto CTS function is enabled
through the enhanced feature register (EFR[7]), for hardware flow control operation.
D0–D4,
D5–D7
44–48,
1–3
27–31
32, 1, 2
I/O
Data bus (bidirectional). These pins are the eight-bit, 3-state data bus for transferring
information to or from the controlling CPU. D0 is the least significant bit and the first data
bit in a transmit or receive serial data stream.
DSRA, DSRB,
39, 20
I
Data set ready (active low). These inputs are associated with individual UART channels
A through B. A low on these pins indicates the modem or data set is powered on and is
ready for data exchange with the UART.
Data terminal ready (active low). These outputs are associated with individual UART
channels A through B. A low on these pins indicates that the TL16C752C is powered on
and ready. These pins can be controlled through the modem control register. Writing a 1
to MCR[0] sets the DTR output to low, enabling the modem. The output of these pins is
high after writing a 0 to MCR[0], or after a reset. These pins can also be used in the
RS-485 mode to control an external RS-485 driver or transceiver.
DTRA, DTRB,
GND
34, 35
22, 23
O
17
12
Pwr
Power signal and power ground
30, 29
20, 19
O
Interrupt A and B (active high). These pins provide individual channel interrupts, INTA-D.
INTA−D are enabled when MCR[3] is set to a 1, interrupts are enabled in the interrupt
enable register (IER) and when an interrupt condition exists. Interrupt conditions include:
receiver errors, available receiver buffer data, transmit buffer empty, or when a modem
status flag is detected. INTA−D are in the high-impedance state after reset.
IOR
19
13
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Read input (active low strobe). A valid low level on IOR loads the contents of an internal
register defined by address bits A0–A2 onto the TL16C752C data bus (D0–D7) for
access by an external CPU.
IOW
15
11
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Write input (active low strobe). A valid low level on IOW transfers the contents of the
data bus (D0–D7) from the external CPU to an internal register that is defined by
address bits A0–A2.
NC
12, 24
35, 37
No internal connection
32, 9
O
User defined outputs. This function is associated with individual channels A and B. The
state of these pins is defined by the user through the software settings of the MCR
register, bit 3. INTA-B are set to active mode and OP to a logic 0 when the MCR-3 is set
to a logic 1. INTA-B are set to the 3-state mode and OP to a logic 1 when MCR-3 is set
to a logic 0. See bit 3, modem control register (MCR bit 3). The output of these two pins
is high after reset.
I
Reset. RESET resets the internal registers and all the outputs. The UART transmitter
output and the receiver input are disabled during reset time. See TL16C752C external
reset conditions for initialization details. RESET is an active high input.
I
Ring indicator (active low). These inputs are associated with individual UART channels A
and B. A logic low on these pins indicates the modem has received a ringing signal from
the telephone line. A low-to-high transition on these input pins generates a modem
status interrupt, if enabled. The state of these inputs is reflected in the modem status
register (MSR).
INTA, INTB,
OPA, OPB
RESET
RIA, RIB,
36
24
41, 21
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DUAL UART
WITH 64-BYTE FIFO
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SLLS646 – MARCH 2008
TERMINAL FUNCTIONS (continued)
TERMINAL
NO.
NAME
PFB
RTSA, RTSB,
33, 22
I/O
DESCRIPTION
O
Request to send (active low). These outputs are associated with individual UART
channels A through D. A low on the RTS pins indicates the transmitter has data ready
and waiting to send. Writing a 1 in the modem control register (MCR[1]) sets these pins
to low, indicating data is available. After a reset, these pins are set to 1. These pins only
affect the transmit and receive operation when auto-RTS function is enabled through the
enhanced feature register (EFR[6]), for hardware flow control operation.
I
Receive data input. These inputs are associated with individual serial channel data to
the TL16C752C. During the local loopback mode, these RX input pins are disabled and
TX data is internally connected to the UART RX input internally. During normal mode,
RXn should be held high when no data is being received. These outputs also can be
used in IrDA mode. See the IrDA mode section for more information.
O
Receive ready (active low). RXRDYA and RXRDYB go low when the trigger level has
been reached or a timeout interrupt occurs. They go high when the RX FIFO is empty or
there is an error in RX FIFO.
O
Transmit data. These outputs are associated with individual serial transmit channel data
from the TL16C752C. During the local loopback mode, the TX input pin is disabled and
TX data is internally connected to the UART RX input.
O
Transmit ready (active low). TXRDYA and TXRDYB go low when there are a trigger
level number of spares available. They go high when the TX buffer is full.
RHB
21, 14
RXA, RXB,
5, 4
RXRDYA,
RXRDYB
31, 18
TXA, TXB,
7, 8
TXRDYA,
TXRDYB
43, 6
VCC
6, 42
4, 26
Pwr
XTAL1
13
9
I
Crystal or external clock input. XTAL1 functions as a crystal input or as an external clock
input. A crystal can be connected between XTAL1 and XTAL2 to form an internal
oscillator circuit (see Figure 10). Alternatively, an external clock can be connected to
XTAL1 to provide custom data rates.
XTAL2
14
10
O
Output of the crystal oscillator or buffered clock. See also XTAL1. XTAL2 is used as a
crystal oscillator output or buffered clock output.
4
4, 3
5, 6
Power supply inputs
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DUAL UART
WITH 64-BYTE FIFO
www.ti.com
SLLS646 – MARCH 2008
FUNCTIONAL BLOCK DIAGRAM
UART Channel A
TXA
A2 – A0
16-Byte Tx FIFO
D7 – D0
Tx
CTSA
OPA, DTRA
CSA
UART Regs
CSB
BAUD
Rate
Gen
IOR
IOW
DSRA, RIA, CDA
RTSA
16-Byte Rx FIFO
Rx
RXA
INTA
INTB
TXRDYA
Data Bus
Interface
UART Channel B
TXRDYB
TXB
16-Byte Tx FIFO
RXRDYA
Tx
RXRDYB
OPB, DTRB
UART Regs
BAUD
Rate
Gen
RESET
XTAL1
XTAL2
CTSB
DSRB, RIB, CDB
RTSB
16-Byte Rx FIFO
Crystal
OSC
Buffer
Rx
RXB
VCC
GND
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DUAL UART
WITH 64-BYTE FIFO
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A.
The vote logic determines whether the RX data is a logic 1 or 0. It takes three samples of the RX line and uses a
majority vote to determine the logic level received. The Vote logic operates on all bits received.
FUNCTIONAL DESCRIPTION
The TL16C752C UART is pin compatible with the TL16C2550 UART in the PFB package. It provides more
enhanced features. All additional features are provided through a special enhanced feature register.
The UART performs serial-to-parallel conversion on data characters received from peripheral devices or modems
and parallel-to-parallel conversion on data characters transmitted by the processor. The complete status of each
channel of the TL16C752C UART can be read at any time during functional operation by the processor.
The TL16C752C UART can be placed in an alternate mode (FIFO mode) relieving the processor of excessive
software overhead by buffering received/transmitted characters. Both the receiver and transmitter FIFOs can
store up to 64 bytes (including three additional bits of error status per byte for the receiver FIFO) and have
selectable or programmable trigger levels. Primary outputs RXRDY and TXRDY allow Signaling of DMA
transfers.
The TL16C752C UART has selectable hardware flow control and software flow control. Both schemes
significantly reduce software overhead and increase system efficiency by automatically controlling serial data
flow. Hardware flow control uses the RTS output and CTS input signals. Software flow control uses
programmable Xon/Xoff characters.
The TL16C752C includes a programmable baud rate generator that can divide the timing reference clock by a
divisor between 1 and 65535. A bit (MCR7) can be used to invoke a pre-scaler (divide by 4) off the reference
clock, prior to the baud rate generator input. The divide by 4 pre-scaler is selected when MCR7 is set to 1.
Trigger Levels
The TL16C752C UART provides independent selectable and programmable trigger levels for both receiver and
transmitter DMA and interrupt generation. After reset, both transmitter and receiver FIFOs are disabled and so, in
effect, the trigger level is the default value of one byte. The selectable trigger levels are available via the FCR.
The programmable trigger levels are available via the TLR.
6
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Hardware Flow Control
Hardware flow control is composed of auto-CTS and auto-RTS. Auto-CTS and auto-RTS can be
enabled/disabled independently by programming EFR[7:6].
With auto-CTS, CTS must be active before the UART can transmit data. Auto-RTS only activates the RTS output
when there is enough room in the FIFO to receive data and deactivates the RTS output when the RX FIFO is
sufficiently full. The HALT and RESTORE trigger levels in the TCR determine the levels at which RTS is
activated/deactivated. If both auto-CTS and auto-RTS are enabled, when RTS is connected to CTS, data
transmission does not occur unless the receiver FIFO has empty space. Thus, overrun errors are eliminated
during hardware flow control. If not enabled, overrun errors occur if the transmit data rate exceeds the receive
FIFO servicing latency.
Auto-RTS
Auto-RTS data flow control originates in the receiver block (see functional block diagram). Figure 1 shows RTS
functional timing. The receiver FIFO trigger levels used in Auto-RTS are stored in the TCR. RTS is active if the
RX FIFO level is below the HALT trigger level in TCR[3:0]. When the receiver FIFO HALT trigger level is
reached, RTS is deasserted. The sending device (e.g., another UART) may send an additional byte after the
trigger level is reached (assuming the sending UART has another byte to send) because it may not recognize the
deassertion of RTS until it has begun sending the additional byte. RTS is automatically reasserted once the
receiver FIFO reaches the RESUME trigger level programmed via TCR[7:4]. This reassertion allows the sending
device to resume transmission.
A.
N = receiver FIFO trigger level B.
B.
The two blocks in dashed lines cover the case where an additional byte is sent as described in Auto-RTS.
Figure 1. RTS Functional Timing
Auto-CTS
The transmitter circuitry checks CTS before sending the next data byte. When CTS is active, the transmitter
sends the next byte. To stop the transmitter from sending the following byte, CTS must be deasserted before the
middle of the last stop bit that is currently being sent. The auto-CTS function reduces interrupts to the host
system. When flow control is enabled, the CTS state changes and need not trigger host interrupts because the
device automatically controls its own transmitter. Without auto-CTS, the transmitter sends any data present in the
transmit FIFO and a receiver overrun error can result. Figure 2 shows CTS functional timing, and Figure 3 shows
an example of autoflow control.
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A.
When CTS is low, the transmitter keeps sending serial data out.
B.
When CTS goes high before the middle of the last stop bit of the current byte, the transmitter finishes sending the
current byte, but it does not send the next byte.
C.
When CTS goes from high to low, the transmitter begins sending data again.
Figure 2. CTS Functional Timing
UART 1
UART 2
Serial to
Parallel
RX
TX
Parallel to
Serial
RX
FIFO
TX
FIFO
Flow
Control
RTS CTS
Flow
Control
D7- D0
D7- D0
Parallel to
Serial
TX
RX
Serial to
Parallel
TX
FIFO
RX
FIFO
Flow
Control
CTS RTS
Flow
Control
Figure 3. Autoflow Control (Auto-RTS and Auto-CTS) Example
Software Flow Control
Software flow control is enabled through the enhanced feature register and the modem control register. Different
combinations of software flow control can be enabled by setting different combinations of EFR[3−0]. Table 1
shows software flow control options.
Two other enhanced features relate to S/W flow control:
• Xon Any Function [MCR(5): Operation resumes after receiving any character after recognizing the Xoff
character.
NOTE:
It is possible that an Xon1 character is recognized as an Xon Any character, which
could cause an Xon2 character to be written to the RX FIFO.
•
8
Special Character [EFR(5)]: Incoming data is compared to Xoff2. Detection of the special character sets the
Xoff interrupt {IIR(4)] but does not halt transmission. The Xoff interrupt is cleared by a read of the IIR. The
special character is transferred to the RX FIFO.
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Table 1. Software Flow Control Options EFR[3:0]
BIT 3
BIT 2
BIT 1
BIT 0
0
0
X
X
No transmit flow control
Tx, Rx SOFTWARE FLOW CONTROLS
1
0
X
X
Transmit Xon1, Xoff1
0
1
X
X
Transmit Xon2, Xoff2
1
1
X
X
Transmit Xon1, Xon2: Xoff1, Xoff2
X
X
0
0
No receive flow control
X
X
1
0
Receiver compares Xon1, Xoff1 X X 0 1
X
X
0
1
Receiver compares Xon2, Xoff2
1
0
1
1
Transmit Xon1, Xoff1
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
0
1
1
1
Transmit Xon2, Xoff2
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
1
1
1
1
Transmit Xon1, Xon2: Xoff1, Xoff2
Receiver compares Xon1 and Xon2: Xoff1 and Xoff2
0
0
1
1
No transmit flow control
Receiver compares Xon1 and Xon2: Xoff1 and Xoff2
When software flow control operation is enabled, the TL16C752C compares incoming data with Xoff1/2
programmed characters (in certain cases Xoff1 and Xoff2 must be received sequentially (1)). When an Xoff
character is received, transmission is halted after completing transmission of the current character. Xoff character
detection also sets IIR[4] and causes INT to go high (if enabled via IER[5]).
To resume transmission an Xon1/2 character must be received (in certain cases Xon1 and Xon2 must be
received sequentially). When the correct Xon characters are received IIR[4] is cleared and the Xoff interrupt
disappears.
NOTE:
If a parity, framing or break error occurs while receiving a software flow control
character, this character is treated as normal data and is written to the RCV FIFO.
Xoff1/2 characters are transmitted when the RX FIFO has passed the programmed trigger level TCR[3:0].
Xon1/2 characters are transmitted when the RX FIFO reaches the trigger level programmed via TCR[7:4].
NOTE:
If, after an Xoff character has been sent, software flow control is disabled, the UART
transmits Xon characters automatically to enable normal transmission to proceed. A
feature of the TL16C752C UART design is that if the software flow combination
(EFR[3:0]) changes after an Xoff has been sent, the originally programmed Xon is
automatically sent. If the RX FIFO is still above the trigger level the newly
programmed Xoff1/2 is transmitted.
The transmission of Xoff/Xon(s) follows the exact same protocol as transmission of an ordinary byte from the
FIFO. This means that even if the word length is set to be 5, 6, or 7 characters, then the 5, 6, or 7 least
significant bits of Xoff1,2/Xon1,2 are transmitted. The transmission of 5, 6, or 7 bits of a character is seldom
done, but this functionality is included to maintain compatibility with earlier designs.
It is assumed that software flow control and hardware flow control are never enabled simultaneously. Figure 4
shows a software flow control example.
(1)
When pairs of Xon/Xoff characters are programmed to occur sequentially, received Xon1/Xoff1 characters will be written to the Rx FIFO
if the subsequent character is not Xon2/Xoff2.
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UART 1
UART 2
Transmit
FIFO
Receive
FIFO
Data
Parallel to Serial
Serial to Parallel
Xoff - Xon - Xoff
Serial to Parallel
Parallel to Serial
Xon-1 Word
Xon-1 Word
Xon-2 Word
Xon-2 Word
Xoff-1 Word
Xoff-1 Word
Xoff-1 Word
Compare
Programmed
Xon- Xoff
Characters
Xoff-2 Word
Figure 4. Software Flow Control Example
Software Flow Control Example
Assumptions: UART1 is transmitting a large text file to UART2. Both UARTs are using software flow control with
single character Xoff (0F) and Xon (0D) tokens. Both have Xoff threshold (TCR [3:0]=F) set to 60 and Xon
threshold (TCR[7:4]=8) set to 32. Both have the interrupt receive threshold (TLR[7:4]=D) set to 52.
UART1 begins transmission and sends 52 characters, at which point UART2 generates an interrupt to its
processor to service the RCV FIFO, but assumes the interrupt latency is fairly long. UART1 continues sending
characters until a total of 60 characters have been sent. At this time UART2 transmits a 0F to UART1, informing
UART1 to halt transmission. UART1 will likely send the 61st character while UART2 is sending the Xoff
character. Now UART2 is serviced and the processor reads enough data out of the RCV FIFO that the level
drops to 32. UART2 now sends a 0D to UART1, informing UART1 to resume transmission.
Reset
Table 2 summarizes the state of outputs after reset.
10
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Table 2. Register Reset Functions (1)
REGISTER
RESET
CONTROL
RESET STATE
Interrupt enable register
RESET
All bits cleared
Interrupt identification register
RESET
Bit 0 is set. All other bits cleared.
FIFO control register
RESET
All bits cleared
Line control register
RESET
Reset to 00011101 (1D hex).
Modem control register
RESET
All bits cleared
Line status register
RESET
Bits 5 and 6 set. All other bits cleared.
Modem status register
RESET
Bits 0–3 cleared. Bits 4–7 input signals.
Enhanced feature register
RESET
All bits cleared
Receiver holding register
RESET
Pointer logic cleared
Transmitter holding register
RESET
Pointer logic cleared
Transmission control register
RESET
All bits cleared
Trigger level register
RESET
All bits cleared
Alternate function register
RESET
All bits (except AFR4) cleared; AFR4 set
(1)
Registers DLL, DLH, SPR, Xon1, Xon2, Xoff1, Xoff2 are not reset by the top-level reset signal RESET,
i.e., they hold their initialization values during reset.
Table 3 summarizes the state of outputs after reset.
Table 3. Signal Reset Functions
SIGNAL
RESET CONTROL
RESET STATE
TX
RESET
High
RTS
RESET
High
DTR
RESET
High
RXRDYA–B
RESET
High
TXRDYA–B
RESET
Low
Interrupts
The TL16C752C UART has interrupt generation and prioritization (six prioritized levels of interrupts) capability.
The interrupt enable register (IER) enables each of the six types of interrupts and the INT signal in response to
an interrupt generation. The IER also can disable the interrupt system by clearing bits 0−3, 5−7. When an
interrupt is generated, the interrupt identification register(IIR) indicates that an interrupt is pending and provides
the type of interrupt through IIR[5−0]. Table 4 summarizes the interrupt control functions.
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Table 4. Interrupt Control Functions
IIR[5–0]
PRIORITY
LEVEL
INTERRUPT
TYPE
000001
None
None
000110
1
Receiver line
status
001100
2
RX timeout
000100
2
RHR interrupt
DRDY (data ready)
Read RHR
(FIFO disable)
RX FIFO above trigger level (FIFO enable)
000010
3
THR interrupt
TFE (THR empty)
(FIFO disable)
TX FIFO passes above trigger level (FIFO
enable)
Read IIR or a write to the THR
000000
4
Modem status
MSR[3:0]= 0
Read MSR
010000
5
Xoff interrupt
Receive Xoff character(s)/special character Receive Xon character(s)/Read of IIR
100000
6
CTS, RTS
INTERRUPT SOURCE
INTERRUPT RESET METHOD
None
None
OE, FE, PE, or BI errors occur in
characters in the RX FIFO
FE < PE < BI: All erroneous characters are
read from the RX FIFO. OE: Read LSR
Stale data in RX FIFO
Read RHR
RTS pin or CTS pin change state from
active (low) to inactive (high)
Read IIR
It is important to note that for the framing error, parity error, and break conditions, LSR[7] generates the interrupt.
LSR[7] is set when there is an error anywhere in the RX FIFO and is cleared only when there are no more errors
remaining in the FIFO. LSR[4–2] always represent the error status for the received character at the top of the Rx
FIFO. Reading the Rx FIFO updates LSR[4–2] to the appropriate status for the new character at the top of the
FIFO. If the Rx FIFO is empty, then LSR[4–2] is all zeros.
For the Xoff interrupt, if an Xoff flow character detection caused the interrupt, the interrupt is cleared by an Xon
flow character detection. If a special character detection caused the interrupt, the interrupt is cleared by a read of
the ISR.
Interrupt Mode Operation
In interrupt mode (if any bit of IER[3:0] is1), the processor is informed of the status of the receiver and transmitter
by an interrupt signal, INT. Therefore, it is not necessary to continuously poll the line status register (LSR) to see
if any interrupt needs to be serviced. Figure 5 shows interrupt mode operation.
Figure 5. Interrupt Mode Operation
Polled Mode Operation
In polled mode (IER[3:0] = 0000), the status of the receiver and transmitter can then be checked by polling the
line status register (LSR). This mode is an alternative to the interrupt mode of operation where the status of the
receiver and transmitter is automatically known by means of interrupts sent to the CPU. Figure 6 shows polled
mode operation.
12
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Figure 6. FIFO Polled Mode Operation
DMA Signaling
There are two modes of DMA operation, DMA mode 0 or 1, selected by FCR[3].
In DMA mode 0 or FIFO disable (FCR[0]=0) DMA occurs in single character transfers. In DMA mode 1
multicharacter (or block) DMA transfers are managed to relieve the processor for longer periods of time.
Single DMA Transfers (DMA Mode0/FIFO Disable)
Transmitter: When empty, the TXRDY signal becomes active. TXRDY goes inactive after one character has
been loaded into it.
Receiver: RXRDY is active when there is at least one character in the FIFO. It becomes inactive when the
receiver is empty.
Figure 7 shows TXRDY and RXRDY in DMA mode 0/FIFO disable.
Figure 7. TXRDY and RXRDY in DMA Mode 0/FIFO Disable
Block DMA Transfers (DMA Mode1)
Transmitter: TXRDY is active when a trigger level number of spaces are available. It becomes inactive when the
FIFO is full.
Receiver: RXRDY becomes active when the trigger level has been reached or when a timeout interrupt occurs. It
goes inactive when the FIFO is empty or an error in the RX FIFO is flagged by LSR(7).
Figure 8 shows TXRDY and RXRDY in DMA mode 1.
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Figure 8. TXRDY and RXRDY in DMA Mode 1
Sleep Mode
Sleep mode is an enhanced feature of the TL16C752C UART. It is enabled when EFR[4], the enhanced
functions bit, is set and when IER[4] is set. Sleep mode is entered when:
• The serial data input line, RX, is idle (see break and time-out conditions).
• The TX FIFO and TX shift register are empty.
• There are no interrupts pending except THR and timeout interrupts.
Sleep mode is not entered if there is data in the RX FIFO.
In sleep mode the UART clock and baud rate clock are stopped. Because most registers are clocked using these
clocks the power consumption is greatly reduced. The UART wakes up when any change is detected on the RX
line, when there is any change in the state of the modem input pins or if data is written to the TX FIFO.
NOTE:
Writing to the divisor latches, DLL and DLH, to set the baud clock, must not be done
during sleep mode. Therefore it is advisable to disable sleep mode using IER[4]
before writing to DLL or DLH.
Break and Timeout Conditions
An RX timeout condition is detected when the receiver line, RX, has been high for a time equivalent to (4 ×
programmed word length) + 12 bits and there is at least one byte stored in the Rx FIFO.
When a break condition occurs, the TX line is pulled low. A break condition is activated by setting LCR[6].
14
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Programmable Baud Rate Generator
The TL16C752C UART contains a programmable baud generator that divides reference clock by a divisor in the
range between 1 and (216−1). The output frequency of the baud rate generator is 16× the baud rate. An
additional divide-by-4 prescaler is also available and can be selected by the CLKSEL pin or MCR[7], as shown in
the following. The formula for the divisor is:
Divisor = (XTAL crystal input frequency / prescaler) / (desired baud rate X 16)
Where
1 when CLKSEL = high during reset, or MCR[7] is set to 0 after reset
prescaler =
4 when CLKSEL = high during reset, or MCR[7] is set to 0 after reset
Figure 9 shows the internal prescaler and baud rate generator circuitry.
Prescaler Logic
(Divide By 1)
XTAL1
XTAL2
Internal
Oscillator
Logic
MCR[7] = 0
Input Clock
Reference
Clock
Prescaler Logic
(Divide By 4)
Bandrate
Generator
Logic
Internal
Bandrate Clock
For Transmitter
and Receiver
MCR[7] = 1
Figure 9. Prescaler and Baud Rate Generator Block Diagram
DLL and DLH must be written to in order to program the baud rate. DLL and DLH are the least significant and
most significant byte of the baud rate divisor. If DLL and DLH are both zero, the UART is effectively disabled, as
no baud clock is generated. The programmable baud rate generator is provided to select both the transmit and
receive clock rates. Table 5 and Table 6 show the baud rate and divisor correlation for the crystal with frequency
1.8432 MHz and 3.072 MHz, respectively.
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Table 5. Baud Rates Using a 1.8432-MHz Crystal
DESIRED
BAUD RATE
DIVISOR USED
TO GENERATE
16× CLOCK
50
2304
75
1536
110
1047
0.026
134.5
857
0.058
150
768
300
384
600
192
1200
96
1800
64
2000
58
2400
48
3600
32
4800
24
7200
16
9600
12
19200
6
38400
3
56000
2
PERCENT ERROR
DIFFERENCE BETWEEN
DESIRED AND ACTUAL
0.69
2.86
Table 6. Baud Rates Using a 3.072-MHz Crystal
16
DESIRED
BAUD RATE
DIVISOR USED
TO GENERATE
16× CLOCK
50
3840
PERCENT ERROR
DIFFERENCE BETWEEN
DESIRED AND ACTUAL
75
2560
110
1745
0.026
134.5
1428
0.034
150
1280
300
640
600
320
1200
160
1800
107
2000
96
2400
80
3600
53
4800
40
7200
27
9600
20
19200
10
38400
5
0.312
0.628
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Figure 10 shows the crystal clock circuit reference.
Ω
Ω
Ω
Ω
Ω
A.
For crystal with fundamental frequency from 1 MHz to 24 MHz
B.
For input clock frequency higher then 24 MHz, the crystal is not allowed and the oscillator must be used, because the
TL16C752C internal oscillator cell can only support the crystal frequency up to 24 MHz.
Figure 10. Typical Crystal Clock Circuits
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ABSOLUTE MAXIMUM RATINGS (1)
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
VCC
Supply voltage range
PARAMETER
–0.5
6
V
VI
Input voltage range
–0.5
VCC + 0.5
V
VO
Output voltage range
V
TA
Operating free-air temperature range
Tstg
Storage temperature range
(1)
–0.5
VCC + 0.5
TL16C752C
0
70
TL16C752CI
–40
85
–65
150
UNIT
°C
°C
Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings
only and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating
conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
TYPICAL PACKAGE THERMAL RESISTANCE DATA
PACKAGE
32-pin QFN RHB
θJA = xx°C/W
θJC = xx°C/W
48-pin TQFP PFB
θJA = xx°C/W
θJC = xx°C/W
TYPICAL PACKAGE WEIGHT
PACKAGE
WEIGHT IN GRAMS
32-pin QFN RHB
0.25
48-pin TQFP PFB
0.30
RECOMMENDED OPERATING CONDITIONS, VCC = 1.8 V ±10%
over operating free-air temperature range (unless otherwise noted)
PARAMETER
VCC
Supply voltage
VI
Input voltage
VIH
High-level input voltage
VIL
Low-level input voltage
VO
Output voltage
IOH
High-level output current
All outputs
IOL
Low-level output current
All outputs
MIN
NOM
MAX
UNIT
1.62
1.8
1.98
V
0
VCC
V
1.4
1.98
V
–0.3
0.4
V
0
VCC
V
0.5
mA
Oscillator/clock speed
1
mA
16
MHz
RECOMMENDED OPERATING CONDITIONS, VCC = 2.5 V ±10%
over operating free-air temperature range (unless otherwise noted)
PARAMETER
VCC
Supply voltage
VI
Input voltage
VIH
MIN
NOM
MAX
UNIT
2.25
2.5
2.75
V
0
VCC
V
High-level input voltage
1.8
2.75
V
VIL
Low-level input voltage
–0.3
0.6
V
VO
Output voltage
0
VCC
IOH
High-level output current
All outputs
1
mA
IOL
Low-level output current
All outputs
2
mA
24
MHz
Oscillator/clock speed
18
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RECOMMENDED OPERATING CONDITIONS, VCC = 3.3 V ±10%
over operating free-air temperature range (unless otherwise noted)
MIN
NOM
MAX
VCC
Supply voltage
PARAMETER
3
3.3
3.6
V
VI
Input voltage
0
VCC
V
VIH
High-level input voltage
VIL
Low-level input voltage
VO
Output voltage
IOH
High-level output current
IOL
Low-level output current
0.7 × VCC
UNIT
V
0.3 × VCC
V
VCC
V
All outputs
1.8
mA
All outputs
3.2
mA
32
MHz
MAX
UNIT
0
Oscillator/clock speed
RECOMMENDED OPERATING CONDITIONS, VCC = 5 V ±10%
over operating free-air temperature range (unless otherwise noted)
PARAMETER
VCC
Supply voltage
VI
Input voltage
MIN
Except XIN
NOM
5.5
V
VCC
V
0
VIH
High-level input voltage
VIL
Low-level input voltage
VO
Output voltage
IOH
High-level output current
All outputs
4
IOL
Low-level output current
All outputs
4
mA
48
MHz
XIN
Except XIN
0.8
0.3 × VCC
XIN
0
Oscillator/clock speed
V
0.7 × VCC
VCC
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V
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ELECTRICAL CHARACTERISTICS, VCC = 1.8 V
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
VOH
High-level output voltage IOH = –0.5 mA
VOL
Low-level output voltage
IOL = 1 mA
II
Input current
VCC = 1.98 V,
VI = 0 to 1.98 V,
VSS = 0,
All other terminals floating
High-impedance state
output current
VCC = 1.98 V,
VO = 0 to 1.98 V,
VSS = 0,
IOZ
Supply current
V
V
10
µA
±20
µA
4.5
mA
7
pF
5
7
pF
6
10
pF
10
15
pF
TYP
MAX
TA = 0°C,
CI(CLK)
Clock input capacitance
CO(CLK)
Clock output capacitance VCC = 0,
f = 1 MHz,
Input capacitance
All other terminals grounded
Output capacitance
CO
UNIT
0.5
SIN, DSR, DCD, CTS, and RI at 2 V,
All other inputs at 0.4 V,
No load on outputs,
CI
MAX
Chip selected in write mode or chip deselect
VCC = 1.98 V,
ICC
TYP
1.3
XTAL1 at 16 MHz,
Baud rate = 1 Mbit/s
5
VSS = 0,
TA = 25°C,
ELECTRICAL CHARACTERISTICS, VCC = 2.5 V
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
VOH
High-level output voltage IOH = –1 mA
1.8
VOL
Low-level output voltage
IOL = 2 mA
II
Input current
VCC = 2.75 V,
VI = 0 to 2.75 V,
VSS = 0,
All other terminals floating
High-impedance state
output current
VCC = 2.75 V,
VO = 0 to 2.75 V,
VSS = 0,
IOZ
Supply current
Clock input capacitance
CO(CLK)
Clock output capacitance VCC = 0,
f = 1 MHz,
Input capacitance
All other terminals grounded
Output capacitance
20
V
10
µA
±20
µA
90
mA
5
7
pF
5
7
pF
6
10
pF
10
15
pF
SIN, DSR, DCD, CTS, and RI at 2 V,
CI(CLK)
CO
0.5
TA = 0°C,
All other inputs at 0.6 V,
No load on outputs,
CI
V
Chip selected in write mode or chip deselect
VCC = 2.75 V,
ICC
UNIT
XTAL1 at 24 MHz,
Baud rate = 1.5 Mbit/s
VSS = 0,
TA = 25°C,
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ELECTRICAL CHARACTERISTICS, VCC = 3.3 V
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
VOH
High-level output voltage
IOH = –1.8 mA
VOL
Low-level output voltage
IOL = 3.2 mA
II
Input current
VCC = 3.6 V,
VI = 0 to 3.6 V,
VSS = 0,
All other terminals floating
High-impedance state
output current
VCC = 3.6 V,
VO = 0 to 3.6 V,
VSS = 0,
IOZ
Supply current
Clock output capacitance
CI
Input capacitance
CO
Output capacitance
V
V
10
µA
±20
µA
16
mA
7
pF
5
7
pF
6
10
pF
10
15
pF
TYP
MAX
TA = 0°C,
XTAL1 at 32 MHz,
Baud rate = 2 Mbit/s
Clock input capacitance
CO(CLK)
UNIT
0.5
SIN, DSR, DCD, CTS, and RI at 2 V,
All other inputs at 0.8 V,
No load on outputs,
CI(CLK)
MAX
Chip selected in write mode or chip deselect
VCC = 3.6 V,
ICC
TYP
2.4
5
VCC = 0,
f = 1 MHz,
All other terminals grounded
VSS = 0,
TA = 25°C,
ELECTRICAL CHARACTERISTICS, VCC = 5 V
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
VOH
High-level output voltage
IOH = –4 mA
4
VOL
Low-level output voltage
IOL = 4 mA
II
Input current
VCC = 5.5 V,
VI = 0 to 5.5 V,
VSS = 0,
All other terminals floating
High-impedance state
output current
VCC = 5.5 V,
VO = 0 to 5.5 V,
VSS = 0,
IOZ
Supply current
CI(CLK)
Clock input capacitance
CO(CLK)
Clock output capacitance
CI
Input capacitance
CO
Output capacitance
V
0.4
V
10
µA
±20
µA
40
mA
5
7
pF
5
7
pF
6
10
pF
10
15
pF
Chip selected in write mode or chip deselect
VCC = 5.5 V,
ICC
UNIT
TA = 0°C,
SIN, DSR, DCD, CTS, and RI at 2 V,
All other inputs at 0.8 V,
No load on outputs,
XTAL1 at 48 MHz,
Baud rate = 3 Mbit/s
VCC = 0,
f = 1 MHz,
All other terminals grounded
VSS = 0,
TA = 25°C,
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TYPICAL CHARACTERISTICS
All channels active
3.0
Div = 1
VCC = 2.5 V,
TA = 25°C
TA = 25°C
5
Div = 10
2.0
1.5
1.0
Supply Current, ICC (mA)
2.5
Supply Current, ICC (mA)
6
Div = 1
VCC = 1.8 V,
0.5
Div = 10
4
3
2
1
0.0
0.0
0
0.3
0.6
0.9
1.2
1.5
0.0
1.8
0.7
1.4
Frequency, f (MHz)
Figure 11. Supply Current vs Frequency (VCC = 1.8 V)
3.5
4.2
30
VCC = 5 V,
VCC = 3.3 V,
TA = 25°C
Div = 1
TA = 25°C
25
Div = 10
8
6
4
Supply Current, ICC (mA)
10
Supply Current, ICC (mA)
2.8
Figure 12. Supply Current vs Frequency (VCC = 2.5 V)
12
Div = 1
Div = 10
20
15
10
5
2
0
0
0.0
1.4
2.8
4.2
5.6
7.0
8.4
0
4
8
12
16
20
24
Frequency, f (MHz)
Frequency, f (MHz)
Figure 13. Supply Current vs Frequency (VCC = 3.3 V)
22
2.1
Frequency, f (MHz)
Figure 14. Supply Current vs Frequency (VCC = 5 V)
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TIMING REQUIREMENTS
TA = 0°C to 70°C, VCC = 1.8 V to 5 V ±10% (unless otherwise noted)
LIMITS
TEST
CONDITIONS
PARAMETER
tRES
Reset pulse width
1.8 V
2.5 V
3.3 V
5V
MIN MAX
MIN MAX
MIN MAX
MIN MAX
UNIT
200
200
200
200
ns
63
42
32
20
ns
ET
CP
CP Clock period
t3w
Oscillator/Clock speed
t6s
Address setup time
t6h
Address hold time
t7w
16
24
32
48
MHz
20
15
10
5
ns
See Figure 15 and Figure 16
15
10
7
5
ns
IOR strobe width
See Figure 15 and Figure 16
85
70
50
40
ns
t9d
Read cycle delay
See Figure 16
85
t12d
Delay from IOR to data
See Figure 16
t12h
Data disable time
t13w
IOW strobe width
See Figure 15
85
70
50
40
ns
t15d
Write cycle delay
See Figure 15
85
70
60
50
ns
t16s
Data setup time
See Figure 15
40
30
20
15
ns
t16h
Data hold time
See Figure 15
35
t17d
Delay from IOW to output
50 pF load, See Figure 17
60
40
30
20
ns
t18d
Delay to set interrupt from
MODEM input
50 pF load, See Figure 17
70
55
45
35
ns
t19d
Delay to reset interrupt from
IOR
50 pF load
80
55
40
30
ns
t20d
Delay from stop to set interrupt
See Figure 18
1
1
1
1
Baudrate
t21d
Delay from IOR to reset
interrupt
50 pF load, See Figure 18
55
45
35
25
ns
t22d
Delay from stop to interrupt
See Figure 21
1
1
1
1
Baudrate
t23d
Delay from initial IOW reset to
transmit star
See Figure 21
24
Baudrate
t24d
Delay from IOW to reset
interrupt
See Figure 21
t25d
Delay from stop to set RXRDY
t26d
t27d
Delay from IOW to set TXRDY
t28d
8
70
60
50
ns
65
50
35
25
ns
35
25
20
15
ns
25
24
8
15
24
8
10
24
8
ns
75
45
35
25
ns
See Figure 19 and Figure 20
1
1
1
1
Baudrate
Delay from IOR to reset RXRDY See Figure 19 and Figure 20
1
1
1
1
µs
See Figure 22 and Figure 23
70
60
50
40
ns
Delay from start to reset TXRDY See Figure 22 and Figure 23
16
16
16
16
Baudrate
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Figure 15. General Write Timing
A[2:0]
Valid Address
Valid Address
t6s
t6s
t6h
t6h
t7w
CS
t9d
t7w
IOR
t12d
t12h
t12d
t12h
D[7:0]
Figure 16. General Read Timing
24
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IOW
RTS (A–B)
DTR (A–B)
CD (A–B)
CTS (A–B)
DSR (A–B)
INT (A–B)
IOR
RI (A–B)
Figure 17. Modem/Output Timing
Stop
Bit
Start
Bit
Data Bits (5–8)
RX (A–B)
D0
D1
D3
D2
D4
D5
5 Data Bits
6 Data Bits
7 Data Bits
D6
D7
Parity
Bit
Next
Data
Start
Bit
t20d
INT (A–B)
Active
t21d
Active
IOR
16-Baud Rate Clock
Figure 18. Receive Timing
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RX (A–B)
RXRDY (A–B)
RXRDY
IOR
Figure 19. Receive Ready Timing in None FIFO Mode
RX (A–B)
RXRDY (A–B)
RXRDY
IOR
Figure 20. Receive Timing in FIFO Mode
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TX (A–B)
INT (A–B)
IOW
16-Baud Rate Clock
Figure 21. Transmit Timing
Stop
Bit
Start
Bit
Data Bits (5–8)
D0
TX (A–B)
D1
D2
D3
D4
D5
D6
D7
Next
Data
Start
Bit
Parity
Bit
IOW
D0–D7
Active
Byte 1
t28d
T27d
Active
Transmitter Ready
TXRDY (A–B)
TXRDY
Transmitter
Not Ready
Figure 22. Transmit Ready Timing in None FIFO Mode
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TX (A–B)
IOW
D0–D7
TXRDY (A–B)
TXRDY
Figure 23. Transmit Timing in FIFO Mode
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PRINCIPLES OF OPERATION
Register Map
Each register is selected using address lines A[0], A[1], A[2] and, in some cases, bits from other registers. The
programming combinations for register selection are shown in Table 7.
Table 7. Register Map – Read/Write Properties (1)
(1)
A[2]
A[1]
A[0]
READ MODE
WRITE MODE
0
0
0
Receive holding register (RHR)
Transmit holding register (THR)
0
0
1
Interrupt enable register (IER)
Interrupt enable register
0
1
0
Interrupt identification register (IIR)
FIFO control register (FCR)
0
1
1
Line control register (LCR)
Line control register
1
0
0
Modem control register (MCR)
Modem control register
1
0
1
Line status register (LSR)
1
1
0
Modem status register (MSR)
1
1
1
Scratch register (SPR)
Scratch register (SPR)
0
0
0
Divisor latch LSB (DLL)
Divisor latch LSB (DLL)
0
0
1
Divisor latch MSB (DLH)
Divisor latch MSB (DLH)
1
0
0
Alternate function register (AFR)
Alternate function register (AFR)
0
1
0
Enhanced feature register (EFR)
Enhanced feature register
1
0
0
Xon-1 word
Xon-1 word
1
0
1
Xon-2 word
Xon-2 word
1
1
0
Xoff-1 word
Xoff-1 word
1
1
1
Xoff-2 word
Xoff-2 word
1
1
0
Transmission control register (TCR)
Transmission control register
1
1
1
Trigger level register (TLR)
Trigger level register
1
1
1
FIFO ready register
DLL and DLH are accessible only when LCR bit 7 is 1, and AFR is only accessible when LCR[7:5] = 100.
Enhanced feature register, Xon1, 2 and Xoff1, 2 are accessible only when LCR is set to 10111111 (8hBF).
Transmission control register and trigger level register are accessible only when EFR[4] = 1 and MCR[6] = 1, i.e. EFR[4] and MCR[6]
are read/write enables.
FCR FIFORdy register is accessible when any CS A–D = 0, MCR[2] = 1 and loopback MCR [4] = 0 is disabled.
MCR[7] can only be modified when EFR[4] is set.
Table 8 lists and describes the TL16C752C internal registers.
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Table 8. TL16C752C Internal Registers (1) (2)
SPECIAL
CONSIDERATIONS
ADDR
REGISTER
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
READ/
WRITE
000
RHR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit1
bit 0
Read
000
THR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit1
bit 0
Write
001
IER
CTS
interrupt
enable
RTS
interrupt
enable
Xoff
interrupt
enable
Sleep
mode
Modem
status
interrupt
Rx line
status
interrupt
THR
empty
interrupt
Rx data
available
interrupt
Read/
write
010
FCR
Rx trigger
level
Rx trigger
level
TX trigger
level
TX trigger
level
DMA
mode
select
Resets
Tx FIFO
Resets Rx
FIFO
Enables
FIFOs
Write
010
IIR
FCR(0)
FCR(0)
CTS, RTS
Xoff
Interrupt
priority Bit
2
Interrupt
priority
Bit 1
Interrupt
priority Bit
0
Interrupt
status
Read
011
LCR
DLAB and
EFR
enable
Break
control bit
Sets parity
Parity type
select
Parity
enable
No. of
stop bits
Word
length
Word
length
Read/
write
100
MCR
1× or 4×
clock
TCR and
TLR enable
Xon any
Enable
loopback
IRQ
enable
FIFORdy
Enable
RTS
DTR
Read/
write
101
LSR
Error in Rx
FIFO
THR and
TSR empty
THR
empty
Break
interrupt
Framing
error
Parity
error
Overrun
error
Data in
receiver
Read
110
MSR
CD
RI
DSR
CTS
ΔCD
ΔRI
ΔDSR
ΔCTS
Read
LCR[7] = 0
None
LCR[7:0] ≠
1011 1111
111
SPR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit1
bit 0
Read/
write
000
DLL
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit1
bit 0
Read/
write
001
DLH
bit 15
bit 14
bit 13
bit 12
bit 11
bit 10
bit 9
bit 8
Read/
write
010
AFR
DLY2
DLY1
DLY0
RCVEN
485LG
485RN
IREN
CONC
Read/
write
010
EFR
Auto-CTS
Auto-RTS
Special
character
detect
Enable
enhancedfunctions
S/W flow
control Bit
3
S/W flow
control
Bit 2
S/W flow
control Bit
1
S/W flow
control Bit
0
Read/
write
100
Xon1
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit1
bit 0
Read/
write
101
Xon2
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit1
bit 0
Read/
write
110
Xoff1
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit1
bit 0
Read/
write
111
Xoff2
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit1
bit 0
Read/
write
110
TCR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit1
bit 0
Read/
write
111
TLR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit1
bit 0
Read/
write
111
FIFORdy
RX FIFO
D status
RX FIFO
C status
RX FIFO
B status
RX FIFO
A status
TX FIFO
D status
TX FIFO
C status
TX FIFO
B status
TX FIFO
A status
Read
LCR[7] = 1
LCR[7:5] = 100
LCR[7:0] =
1011 1111
EFR[4] = 1 and
MCR[6] = 1
MCR[4] = 0 and
MCR[2] = 1
(1)
(2)
Bits represented by shaded cells can only be modified if EFR[4] is enabled, i.e., if enhanced functions are enabled.
Refer to the notes under Table 7 for more register access information.
Receiver Holding Register (RHR)
The receiver section consists of the receiver holding register (RHR) and the receiver shift register (RSR). The
RHR is actually a 64-byte FIFO. The RSR receives serial data from RX terminal. The data is converted to parallel
data and moved to the RHR. The receiver section is controlled by the line control register. If the FIFO is disabled,
location zero of the FIFO is used to store the characters. If overflow occurs, characters are lost. The RHR also
stores the error status bits associated with each character.
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Transmit Holding Register (THR)
The transmitter section consists of the transmit holding register (THR) and the transmit shift register (TSR). The
transmit holding register is actually a 64-byte FIFO. The THR receives data and shifts it into the TSR where it is
converted to serial data and moved out on the TX terminal. If the FIFO is disabled, location zero of the FIFO is
used to store the byte. Characters are lost if overflow occurs.
FIFO Control Register (FCR)
This is a write-only register which is used for enabling the FIFOs, clearing the FIFOs, setting transmitter and
receiver trigger levels, and selecting the type of DMA Signaling. Table 9 shows FIFO control register bit settings.
Table 9. FIFO Control Register (FCR) Bit Settings
BIT NO.
0
0 = Disable the transmit and receive FIFOs
1 = Enable the transmit and receive FIFOs
1
0 = No change
1 = Clears the receive FIFO and resets it’s counter logic to zero. Will return to zero after clearing FIFO.
2
0 = No change
1 = Clears the transmit FIFO and resets it’s counter logic to zero. Will return to zero after clearing FIFO.
3
0 = DMA Mode 0
1 = DMA Mode 1
5:4
(1)
7:6
(1)
BIT SETTINGS
Sets the trigger level for the TX FIFO:
00 – 8 spaces
01 – 16 spaces
10 – 32 spaces
11 – 56 spaces
Sets the trigger level for the RX FIFO:
00 – 1 characters
01 – 4 characters
10 – 56 characters
11 – 60 characters
FCR[5−4] can be modified and enabled only when EFR[4] is set. This is because the transmit trigger level is regarded as an enhanced
function.
Line Control Register (LCR)
This register controls the data communication format. The word length, number of stop bits, and parity type are
selected by writing the appropriate bits to the LCR. Table 10 shows line control register bit settings.
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Table 10. Line Control Register (LCR) Bit Settings
BIT NO.
1:0
BIT SETTINGS
Specifies the word length to be transmitted or received.
00 – 5 bits
01 – 6 bits
10 − 7 bits
11 – 8 bits
2
Specifies the number of stop bits:
0 – 1 stop bits (Word length = 5, 6, 7, 8)
1 – 1.5 stop bits (Word length = 5)
1 – 2 stop bits (Word length = 6, 7, 8) 3
3
0 = No parity
1 = A parity bit is generated during transmission and the receiver checks for received parity.
4
0 = Odd parity is generated (if LCR[3] = 1)
1 = Even parity is generated (if LCR[3] = 1)
5
Selects the forced parity format (if LCR(3) = 1)
If LCR[5] = 1 and LCR[4] = 0 the parity bit is forced to 1 in the transmitted and received data.
If LCR[5] = 1 and LCR[4] = 1 the parity bit is forced to 0 in the transmitted and received data.
6
Break control bit.
0 = Normal operating condition
1 = Forces the transmitter output to go low to alert the communication terminal.
7
0 = Normal operating condition
1 = Divisor latch enable
Line Status Register (LSR)
Table 11 shows line status register bit settings.
Table 11. Line Status Register (LSR) Bit Settings
BIT NO.
BIT SETTINGS
0
0 = No data in the receive FIFO
1 = At least one character in the RX FIFO
1
0 = No overrun error
1 = Overrun error has occurred.
2
0 = No parity error in data being read from RX FIFO
1 = Parity error in data being read from RX FIFO
3
0 = No framing error in data being read from RX FIFO
1 = Framing error occurred in data being read from RX FIFO (i.e., received data did not have a valid stop bit)
4
0 = No break condition
1 = A break condition occurred and associated byte is 00. (i.e., RX was low for at least one character time frame).
5
0 = Transmit hold register is NOT empty
1 = Transmit hold register is empty. The processor can now load up to 64 bytes of data into the THR if the TX FIFO is
enabled.
6
0 = Transmitter hold AND shift registers are not empty.
1 = Transmitter hold AND shift registers are empty.
7
0 = Normal operation
1 = At least one parity error, framing error or break indication are stored in the receiver FIFO. Bit 7 is cleared when no
errors are present in the FIFO.
When the LSR is read, LSR[4:2] reflects the error bits [BI, FE, PE] of the character at the top of the RX FIFO
(next character to be read). The LSR[4:2] registers do not physically exist, as the data read from the RX FIFO is
output directly onto the output data-bus, DI[4:2], when the LSR is read. Therefore, errors in a character are
identified by reading the LSR and then reading the RHR.
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LSR[7] is set when there is an error anywhere in the RX FIFO and is cleared only when there are no more errors
remaining in the FIFO.
NOTE:
Reading the LSR does not cause an increment of the RX FIFO read pointer. The RX
FIFO read pointer is incremented by reading the RHR.
Modem Control Register (MCR)
The MCR controls the interface with the modem, data set, or peripheral device that is emulating the modem.
Table 12 shows modem control register bit settings.
Table 12. Modem Control Register (MCR) Bit Settings (1)
BIT NO.
(1)
BIT SETTINGS
0
0 = Force DTR output to inactive (high)
1 = Force DTR output to active (low). In loopback controls MSR[5].
1
0 = Force RTS output to inactive (high)
1 = Force RTS output to active (low).
In loopback controls MSR[4].
If Auto-RTS is enabled the RTS output is controlled by hardware flow control
2
0 Disables the FIFORdy register
1 Enable the FIFORdy register.
In loopback controls MSR[6].
3
0 = Forces the IRQ(A–D) outputs to high-impedance state
1 = Forces the IRQ(A–D) outputs to the active state.
In loopback controls MSR[7].
4
0 = Normal operating mode
1 = Enable local loopback mode (internal)
In this mode the MCR[3:0] signals are looped back into MSR[3:0] and the TX output is looped back to the RX input
internally.
5
0 = Disable Xon Any function
1 = Enable Xon Any function
6
0 = No action
1 = Enable access to the TCR and TLR registers.
7
0 = Divide by one clock input
1 = Divide by four clock input
This bit reflects the inverse of the CLKSEL pin value at the trailing edge of the RESET pulse.
MCR[7:5] can be modified only when EFR[4] is set i.e., EFR[4] is a write enable.
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Modem Status Register (MSR)
This 8-bit register provides information about the current state of the control lines from the modem, data set, or
peripheral device to the processor. It also indicates when a control input from the modem changes state.
Table 13 shows modem status register bit settings.
Table 13. Modem Status Register (MSR) Bit Settings (1)
BIT NO.
(1)
BIT SETTINGS
0
Indicates that CTS input (or MCR[1] in loopback) has changed state. Cleared on a read.
1
Indicates that DSR input (or MCR[0] in loopback) has changed state. Cleared on a read.
2
Indicates that RI input (or MCR[2] in loopback) has changed state from low to high. Cleared on a read.
3
Indicates that CD input (or MCR[3] in loopback) has changed state. Cleared on a read.
4
This bit is equivalent to MCR[1] during local loop-back mode. It is the complement to the CTS input.
5
This bit is equivalent to MCR[0] during local loop-back mode. It is the complement to the DSR input.
6
This bit is equivalent to MCR[2] during local loop-back mode. It is the complement to the RI input.
7
This bit is equivalent to MCR[3] during local loop-back mode. It is the complement to the CD input.
The primary inputs RI, CD, CTS, DSR are all active low but their registered equivalents in the MSR and MCR (in loopback) registers are
active high.
Interrupt Enable Register (IER)
The interrupt enable register (IER) enables each of the six types of interrupt, receiver error, RHR interrupt, THR
interrupt, Xoff received, or CTS/RTS change of state from low to high. The INT output signal is activated in
response to interrupt generation. Table 14 shows interrupt enable register bit settings.
Table 14. Interrupt Enable Register (IER) Bit Settings (1)
BIT NO.
(1)
34
BIT SETTINGS
0
0 = Disable the RHR interrupt
1 = Enable the RHR interrupt
1
0 = Disable the THR interrupt
1 = Enable the THR interrupt
2
0 = Disable the receiver line status interrupt
1 = Enable the receiver line status interrupt
3
0 = Disable the modem status register interrupt
1 = Enable the modem status register interrupt
4
0 = Disable sleep mode
1 = Enable sleep mode
5
0 = Disable the Xoff interrupt
1 = Enable the Xoff interrupt
6
0 = Disable the RTS interrupt
1 = Enable the RTS interrupt
7
0 = Disable the CTS interrupt
1 = Enable the CTS interrupt
IER[7:4] can be modified only if EFR[4] is set, i.e., EFR[4] is a write enable.
Re-enabling IER[1] causes a new interrupt, if the THR is below the threshold.
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Interrupt Identification Register (IIR)
The IIR is a read-only 8-bit register which provides the source of the interrupt in a prioritized manner. Table 15
shows interrupt identification register bit settings.
Table 15. Interrupt Identification Register (IIR) Bit
Settings
BIT NO.
0
3:1
BIT SETTINGS
0 = An interrupt is pending
1 = No interrupt is pending
3-Bit encoded interrupt. See Table 14.
4
1 = Xoff/Special character has been detected.
5
CTS/RTS low to high change of state
7:6
Mirror the contents of FCR[0]
The interrupt priority list is illustrated in Table 16.
Table 16. Interrupt Priority List
PRIORITY
LEVEL
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
1
0
0
0
1
1
0
Receiver line status error
2
0
0
1
1
0
0
Receiver timeout interrupt
2
0
0
0
1
0
0
RHR interrupt
3
0
0
0
0
1
0
THR interrupt
4
0
0
1
0
0
0
Modem interrupt
5
0
1
0
0
0
0
Received Xoff signal/special character
6
1
0
0
0
0
0
CTS, RTS change of state from active (low) to inactive (high)
INTERRUPT SOURCE
Enhanced Feature Register (EFR)
This 8-bit register enables or disables the enhanced features of the UART. Table 17 shows the enhanced feature
register bit settings.
Table 17. Enhanced Feature Register (EFR) Bit Settings
BIT NO.
3:0
BIT SETTINGS
Combinations of software flow control can be selected by programming bit 3−bit 0. See Table 1.
4
Enhanced functions enable bit.
0 = Disables enhanced functions and writing to IER[7:4], FCR[5:4], MCR[7:5].
1 = Enables the enhanced function IER[7:4], FCR[5:4], and MCR[7:5] can be modified, i.e., this bit is therefore a write
enable.
5
0 = Normal operation
1 = Special character detect. Received data is compared with Xoff-2 data. If a match occurs, the received data is
transferred to FIFO and IIR[4] is set to 1 to indicate a special character has been detected.
6
RTS flow control enable bit
0 = Normal operation
1 = RTS flow control is enabled i.e., RTS pin goes high when the receiver FIFO HALT trigger level TCR[3:0] is reached,
and goes low when the receiver FIFO RESTORE transmission trigger level TCR[7:4] is reached.
7
CTS flow control enable bit
0 = Normal operation
1 = CTS flow control is enabled i.e., transmission is halted when a high signal is detected on the CTS pin.
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Divisor Latches (DLL, DLH)
Two 8-bit registers store the 16-bit divisor for generation of the baud clock in the baud rate generator. DLH,
stores the most significant part of the divisor. DLL stores the least significant part of the division.
DLL and DLH can only be written to before sleep mode is enabled (i.e., before IER[4] is set).
Transmission Control Register (TCR)
This 8-bit register is used to store the receive FIFO threshold levels to start/stop transmission during
hardware/software flow control. Table 18 shows transmission control register bit settings.
Table 18. Transmission Control Register (TCR) Bit
Settings
BIT NO.
BIT SETTINGS
3:0
RCV FIFO trigger level to HALT transmission (0–60)
7:4
RCV FIFO trigger level to RESTORE transmission (0–60)
TCR trigger levels are available from 0–60 bytes with a granularity of four.
TCR can be written to only when EFR[4] = 1 and MCR[6] = 1. The programmer must program the TCR such that
TCR[3:0] > TCR[7:4]. There is no built-in hardware check to make sure this condition is met. Also, the TCR must
be programmed with this condition before Auto-RTS or software flow control is enabled to avoid spurious
operation of the device.
Trigger Level Register (TLR)
This 8-bit register is used to store the transmit and received FIFO trigger levels used for DMA and interrupt
generation. Trigger levels from 4−60 can be programmed with a granularity of 4. Table 19 shows trigger level
register bit settings.
Table 19. Trigger Level Register (TLR) Bit Settings
BIT NO.
BIT SETTINGS
3:0
Transmit FIFO trigger levels (4–60), number of spaces
available
7:4
RCV FIFO trigger levels (4–60), number of characters
available
TLR can be written to only when EFR[4] = 1 and MCR[6] = 1. If TLR[3:0] or TLR[7:4] are zero, then the
selectable trigger levels via the FIFO control register (FCR) are used for the transmit and receive FIFO trigger
levels. Trigger levels from 4–60 bytes are available with a granularity of four. The TLR should be programmed for
N/4, where N is the desired trigger level.
FIFO Ready Register
The FIFO ready register provides real-time status of the transmit and receive FIFOs of both channels. Table 20
shows the FIFO ready register bit settings. The trigger level mentioned in Table 20 refers to the setting in either
FCR (when TLR value is zero), or TLR (when it has a nonzero value).
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Table 20. FIFO Ready Register
BIT NO.
BIT SETTINGS
0
0 = There are fewer than a TX trigger level number of spaces available in the TX FIFO of channel A.
1 = There are at least a TX trigger level number of spaces available in the TX FIFO of channel A.
1
0 = There are fewer than a TX trigger level number of spaces available in the TX FIFO of channel B.
1 = There are at least a TX trigger level number of spaces available in the TX FIFO of channel B.
3:2
Unused, always 0
4
0 = There are fewer than a RX trigger level number of characters in the RX FIFO of channel A.
1 = The RX FIFO of channel A has more than a RX trigger level number of characters available for reading or a timeout
condition has occurred.
5
0 = There are fewer than a RX trigger level number of characters in the RX FIFO of channel B.
1 = The RX FIFO of channel B has more than a RX trigger level number of characters available for reading or a timeout
condition has occurred.
7:6
Unused, always 0
The FIFORdy register is a read only register and can be accessed when any of the two UARTs are selected.
CSA or CSB = 0, MCR[2] (FIFORdy Enable) is a logic 1, and loopback is disabled. Its address is 111.
Alternate Function Register (AFR)
The alternate function register (AFR) is used to enable some extra functionality beyond the capabilities of the
original TL16C752B. The first of these is a concurrent write mode, which can be useful in more expediently
setting up all four UART channels. The second addition is the IrDA mode, which supports Standard IrDA (SIR)
mode with baud rates from 2400 to 115.2 bps. The third addition is support for RS-485 bus drivers or
transceivers by providing an output pin (DTRx) per channel, which is timed to keep the RS-485 driver enabled as
long as transmit data is pending.
The AFR is located at A[2:0] = 010 when LCR[7:5] = 100.
Table 21. Alternate Function (AF) Bit Settings
BIT NO.
BIT SETTINGS
0
CONC enables the concurrent write of all four (754) or two (752) channels simultaneously, which helps speed up
initialization. Ensure that any indirect addressing modes have been enabled before using.
1
IREN enables the IrDA SIR mode. This mode is only specified to 115.2 bps and use of this mode at higher speeds is not
recommended.
2
485EN enables the half duplex RS-485 mode and causes the DTRx output to be set high whenever there is any data in
the THR or TSR and to be held high until the delay set by DLY3:0 has expired, at which time it will be set low. The DTRx
output is intended to drive the enabled input of an RS-485 driver. When this bit is set, the transmitter interrupts will be
held off until the TSR is empty, unless 485LG is set.
3
485LG is set when the 485EN is set. This bit indicates that a relatively large data block is being set, requiring more than
a single load of the xmt fifo. In this case, the transmitter interrupts occur as in the standard RS-232 mode, either when
the xmt fifo contents drop below the xmt threshold or when the xmt fifo is empty.
4
RCVEN is valid only when 485EN or IREN is set, and allows the serial receiver to listen in or snoop on the RS485 traffic
or IrDA traffic. RS485 mode is generally considered half duplex, and usually a node is either driving or receiving, but
there can be cases when it is advantageous to verify what you are sending. This can be used to detect collisions or as
part of an arbitration mechanism on the bus. When both RCVEN and 485EN are set, the receiver will store any data
presented on RX, if any. Note that implies that the external RS485 receiver is enabled. Whenever 485EN is cleared, the
serial receiver is enabled for normal full duplex RS232 traffic. If RCVEN is cleared while 485EN is set, the receiver will be
disabled. Standard IrDA (SIR) is also considered half duplex. Often the light energy from the transmitting LED is coupled
back into the receiving PIN diode, which creates an input data stream that is not of interest to the host. Disabling the
receiver (clearing RCVEN) prevents this reception, and eliminates the task of unloading the data. On the other hand, for
diagnostic or other purposes, it may be useful to observe this data stream. For example, a mirror could be used to
intentionally couple the output LED to the input PIN. For these cases, RCVEN could be set to enable the receiver.
NOTE: When RCVEN is cleared (set to 0), the character timeout interrupt is not available, even in RSA-232 mode. This
can be useful when checking code for valid threshold interrupts, as the timeout interrupt will not override the threshold
interrupt.
7:5
DLY3–DLY0 sets a delay after the last stop bit of the last data byte being set before the DTRx is set low, to allow for long
cable runs. The delay is in number of bit times and is enabled by 485EN. The delay will start only when both the xmt
serial shift register (TSR) is empty and the xmt fifo (THR) is empty, and if started, will be cleared by any data being
written to the THR.
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Table 22. LOOP and RCVEN Functionality
LOOP MODE
RCVEN
RCVEN = 1
LOOP mode off,
MCR4 = 0,
RX, TX active
RCVEN = 0
RCVEN = 1
LOOP mode on,
MCR4 = 1,
RX, TX inactive
RCVEN = 0
AFR
MODE
DESCRIPTION
AFR = 10
RS-232
Receive threshold, timeout, and error detection interrupts available.
Data stored in receive FIFO.
AFR = 14
RS-485
Receive threshold, timeout, and error detection interrupts available.
Data stored in receive FIFO.
AFR = 12
IrDA
Receive threshold, timeout, and error detection interrupts available.
Data stored in receive FIFO.
AFR = 00
RS-232
Receive threshold and error detection interrupts available.
Data stored in receive FIFO.
AFR = 04
RS-485
No data stored in receive FIFO, hence no interrupts available.
AFR = 02
IrDA
No data stored in receive FIFO, hence no interrupts available.
AFR = 10
RS-232
Receive threshold, timeout, and error detection interrupts available.
Data stored in receive FIFO.
AFR = 14
RS-485
Receive threshold, timeout, and error detection interrupts available.
Data stored in receive FIFO.
AFR = 12
IrDA
Receive threshold, timeout, and error detection interrupts available.
Data stored in receive FIFO.
AFR = 00
RS-232
Receive threshold and error detection interrupts available.
Data stored in receive FIFO.
AFR = 04
RS-485
Receive threshold and error detection interrupts available.
Data stored in receive FIFO.
AFR = 02
IrDA
Receive threshold and error detection interrupts available.
Data stored in receive FIFO.
RS-485 Mode
The RS-485 mode is intended to simplify the interface between the UART channel and an RS-485 driver or
transceiver. When enabled by setting 485EN, the DTRx output goes high one bit time before the first stop bit of
the first data byte being sent, and remains high as long as there is pending data in the transmitter shift register
(TSR) or transmitter holding register (THR, xmt fifo). Once both are empty (after the last stop bit of the last data
byte), the DTRx output stays high for a programmable delay of 0 to 15 bit times, as set by DLY[3:0]. This helps
preserve data integrity over long signal lines. This is illustrated in the following.
Often RS-485 packets are relatively short and the entire packet can fit within the 64 byte xmt fifo. In this case, it
goes empty when the TSR goes empty. But in cases where a larger block needs to be sent, it is advantageous to
reload the xmt fifo as soon as it is depleted. Otherwise, the transmission stalls while waiting for the xmt fifo to be
reloaded, which varies with processor load. In this case, it is best to also set 485LG (large block), which causes
the transmit interrupt to occur wither when the THR becomes empty (if the xmt fifo level was not above the
threshold), or when the xmt fifo threshold is crossed. The reloading of the xmt fifo occurs while some data is
being shifted out, eliminating fifo underrun. If desired, when the last bytes of a current transmission are being
loaded in the xmt fifo, 485LG can be cleared before the load and the transmit interrupt occurs on the TSR going
empty.
38
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WR THR
TX
1 Baud Time
Controlled by DLY[3:0]
DTRx
A.
Waveforms are not shown to scale, as the WR THR pulses typically are less than 100 ns, where the TX waveform
varies with baud rate but is typically in the microsecond range.
Figure 24. DTRx and Transmit Data Relationship
Loopback
Figure 25. RS-485 Application Example 1
RS-485 XCVR
TX
TSR
DTR
Loopback
RS-485 BUS
DEN
REN
RX
RSR
48SEN
RCVEN
UART
Figure 26. RS-485 Application Example 2
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TL16C752C
DUAL UART
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SLLS646 – MARCH 2008
IrDA Overview
Transmit Shift Register
Int_Tx
Tx
To Optoelectronic
LED
Int_Rx
Rx
From
Optoelectronic
Pin Diode
Receive Shift Register
IREN
RCVEN
IrDA Converter
Baud Clock
Reset
Figure 27. IrDA Mode
The infrared data association (IrDA) defines several protocols for sending and receiving serial infrared data,
including rates of 115.2 kbps, 0.576 Mbps, 1.152 Mbps, and 4 Mbps. The low rate of 115.2 kbps was specified
first and the others must maintain downward compatibility with it. At the 115.2 kbps rate, the protocol
implemented in the hardware is fairly simple. It primarily defines a serial infrared data word to be surrounded by a
start bit equal to 0 and a stop bit equal to 1. Individual bits are encoded or decoded the same whether they are
start, data, or stop bits. The IrDA engine in the TL16C752C evaluate only single bits and only follow the 115.2
kbps protocol. The 115.2 kbps rate is a maximum rate. When both ends of the transfer are set up to a lower but
matching speed, the protocol still works. The clock used to code or sample the data is 16 times the baud rate, or
1.843 MHz maximum. To code a 1, no pulse is sent or received for 1-bit time period, or 16 clock cycles. To code
a 0, one pulse is sent or received within a 1-bit time period, or 16 clock cycles. The pulse must be at least 1.6 µs
wide and 3 clock cycles long at 1.843 MHz. At lower baud rates the pulse can be 1.6 µs wide or as long as 3
clock cycles. The transmitter output, Tx, is intended to drive a LED circuit to generate an infrared pulse. The LED
circuits work on positive pulses. A terminal circuit is expected to create the receiver input, Rx. Most, but not all,
PIN circuits have inversion and generate negative pulses from the detected infrared light. Their output is normally
high. The TL16C752C can decode either negative or positive pulses on Rx.
IrDA Encoder Function
Serial data from a UART is encoded to transmit data to the optoelectronics. While the serial data input to this
block (Int_Tx) is high, the output (Tx) is always low, and the counter used to form a pulse on Tx is continuously
cleared. After Int_Tx resets to 0, Tx rises on the falling edge of the seventh 16XCLK. On the falling edge of the
tenth 16XCLK pulse, Tx falls, creating a 3-clock-wide pulse. While Int_Tx stays low, a pulse is transmitted during
the seventh to tenth clocks of each 16-clock bit cycle.
Figure 28. IrDA-SIR Encoding Scheme – Detailed Timing
Diagram
Figure 29. Encoding Scheme – Macro View
After reset, Int_Rx is high and the 4-bit counter is cleared. When a falling edge is detected on Rx, Int_Rx falls on
the next rising edge of 16XCLK with sufficient setup time. Int_Rx stays low for 16 cycles (16XCLK) and then
returns to high as required by the IrDA specification. As long as no pulses (falling edges) are detected on Rx,
Int_Rx remains high.
40
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Figure 30. IrDA-SIR Decoding Scheme – Detailed Timing
Diagram
Figure 31. IrDA-SIR Decoding Scheme – Macro View
It is possible for jitter or slight frequency differences to cause the next falling edge on Rx to be missed for one
16XCLK cycle. In that case, a 1-clock-wide pulse appears on Int_Rx between consecutive zeroes. It is important
for the UART to strobe Int_Rx in the middle of the bit time to avoid latching this 1-clock-wide pulse. The
TL16C550C UART already strobes incoming serial data at the proper time. Otherwise, note that data is required
to be framed by a leading zero and a trailing one. The falling edge of that first zero on Int_Rx synchronizes the
read strobe. The strobe occurs on the eighth 16XCLK pulse after the Int_Rx falling edge and once every 16
cycles thereafter until the stop bit occurs.
Figure 32. Timing Causing 1-Clock-Wide Pulse Between Consecutive Ones
Figure 33. Recommended Strobing for Decoded Data
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TL16C752C
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The TL16C752C can decode positive pulses on Rx. The timing is different, but the variation is invisible to the
UART. The decoder, which works from the falling edge, now recognizes a zero on the trailing edge of the pulse
rather than on the leading edge. As long as the pulse width is fairly constant, as defined by the specification, the
trailing edges should also be 16 clock cycles apart and data can readily be decoded. The zero appears on Int_Rx
after the pulse rather than at the start of it.
Figure 34. Positive Rx Pulse Decode – Detailed View
Figure 35. Positive Rx Pulse Decode – Macro View
42
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TL16C752C Programmer's Guide
The base set of registers that are used during high-speed data transfer have a straightforward access method.
The extended function registers require special access bits to be decoded along with the address lines. The
following guide will help with programming these registers. Note that the descriptions below are for individual
register access. Some streamlining through interleaving can be obtained when programming all the registers.
Set baud rate to VALUE1,VALUE2
Read LCR (03), save in temp
Set LCR (03) to 80
Set DLL (00) to VALUE1
Set DLM (01) to VALUE2
Set LCR (03) to temp
Set Xoff1,Xon1 to VALUE1,VALUE2
Read LCR (03), save in temp
Set LCR (03) to BF
Set Xoff1 (06) to VALUE1
Set Xon1 (04) to VALUE2
Set LCR (03) to temp
Set Xoff2,Xon2 to VALUE1,VALUE2
Read LCR (03), save in temp
Set LCR (03) to BF
Set Xoff2 (07) to VALUE1
Set Xon2 (05) to VALUE2
Set LCR (03) to temp
Set software flow control mode to VALUE
Read LCR (03), save in temp
Set LCR (03) to BF
Set EFR (02) to VALUE
Set LCR (03) to temp
Set flow control threshold to VALUE
Read LCR (03), save in temp1
Set LCR (03) to BF
Read EFR (02), save in temp2
Set EFR (02) to 10 + temp2
Set LCR (03) to 00
Read MCR (04), save in temp3
Set MCR (04) to 40 + temp3
Set TCR (06) to VALUE
Set LCR (03) to BF
Set EFR (02) to temp2
Set LCR (03) to temp1
Set MCR (04) to temp3
Set xmt and rcv FIFO thresholds to VALUE
Read LCR (03), save in temp1
Set LCR (03) to BF
Read EFR (02), save in temp2
Set EFR (02) to 10 + temp2
Set LCR (03) to 00
Read MCR (04), save in temp3
Set MCR (04) to 40 + temp3
Set TLR (07) to VALUE
Set LCR (03) to BF
Set EFR (02) to temp2
Set LCR (03) to temp1
Set MCR (04) to temp3
Read FIFORdy register
Read MCR (04), save in temp1
Set temp2 = temp1 * EF
Set MCR (04), save in temp2
Read FRR (07), save in temp2
Pass temp2 back to host
Set MCR (04) to temp1
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43
PACKAGE OPTION ADDENDUM
www.ti.com
11-Jul-2008
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
TL16C752CIRHBR
ACTIVE
QFN
RHB
32
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-3-260C-168 HR
TL16C752CIRHBRG4
ACTIVE
QFN
RHB
32
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-3-260C-168 HR
TL16C752CRHBR
ACTIVE
QFN
RHB
32
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-3-260C-168 HR
TL16C752CRHBRG4
ACTIVE
QFN
RHB
32
3000 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-3-260C-168 HR
Lead/Ball Finish
MSL Peak Temp (3)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
2-Jul-2008
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
Diameter Width
(mm) W1 (mm)
A0 (mm)
B0 (mm)
K0 (mm)
P1
(mm)
W
Pin1
(mm) Quadrant
TL16C752CIRHBR
QFN
RHB
32
3000
330.0
12.4
5.3
5.3
1.5
8.0
12.0
Q2
TL16C752CRHBR
QFN
RHB
32
3000
330.0
12.4
5.3
5.3
1.5
8.0
12.0
Q2
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
2-Jul-2008
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
TL16C752CIRHBR
QFN
RHB
32
3000
340.5
333.0
20.6
TL16C752CRHBR
QFN
RHB
32
3000
340.5
333.0
20.6
Pack Materials-Page 2
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