TL16C752B-EP Datasheet, PDF (30/35 Pages) Texas Instruments – 3.3-V DUAL UART WITH 64-BYTE FIFO

TL16C752B-EP
3.3-V DUAL UART WITH 64-BYTE FIFO
SGLS153 – FEBRUARY 2003
PRINCIPLES OF OPERATION
interrupt identification register (IIR) (continued)
The interrupt priority list is shown in Table 16.
Table 16. Interrupt Priority List
PRIORITY
LEVEL
1
2
2
3
4
5
6
BIT 5
0
0
0
0
0
0
1
BIT 4
0
0
0
0
0
1
0
BIT 3
0
1
0
0
0
0
0
BIT 2
1
1
1
0
0
0
0
BIT 1
1
0
0
1
0
0
0
BIT 0
INTERRUPT SOURCE
0 Receiver line status error
0 Receiver timeout interrupt
0 RHR interrupt
0 THR interrupt
0 Modem interrupt
0 Received Xoff signal/special character
0 CTS, RTS change of state from active (low) to inactive (high).
enhanced feature register (EFR)
The enhanced feature register is an 8-bit register that 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
4
5
6
7
BIT SETTINGS
Combinations of software flow control can be selected by programming bit 3–bit 0. See Table 1.
Enhanced functions enable bit
0 = Disables enhanced functions and writing to IER bits 4–7, FCR bits 4–5, MCR bits 5–7.
1 = Enables the enhanced function IER bits 4–7, FCR bit 4–5, and MCR bits 5–7 can be modified, i.e., this bit is therefore a
write enable.
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 bit 4 is set to 1 to indicate a special character has been detected.
RTS flow control enable bit
0 = Normal operation
1 = RTS flow control is enabled i.e., the 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.
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.
divisor latches (DLL, DLH)
The divisor lathes are two 8-bit registers which 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.
Note that DLL and DLH can only be written to before sleep mode is enabled (i.e., before IER[4] is set).
transmission control register (TCR)
The transmission control register is an 8-bit register that is used to store the receive FIFO threshold levels to
start/stop transmission during hardware/software flow control. Table 18 shows the transmission control register
bit settings.
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