TL16C752B
3.3-V DUAL UART WITH 64-BYTE FIFO
SLLS405A – DECEMBER 1999 – REVISED AUGUST 2000
PRINCIPLES OF OPERATION
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
BIT NO.
BIT SETTINGS
0 = Disable the RHR interrupt
0
1 = Enable the RHR interrupt
1
2
3
4
5
6
7
0 = Disable the THR interrupt
1 = Enable the THR interrupt
0 = Disable the receiver line status interrupt
1 = Enable the receiver line status interrupt
0 = Disable the modem status register interrupt
1 = Enable the modem status register interrupt
0 = Disable sleep mode
1 = Enable sleep mode
0 = Disable the Xoff interrupt
1 = Enable the Xoff interrupt
0 = Disable the RTS interrupt
1 = Enable the RTS interrupt
0 = Disable the CTS interrupt
1 = Enable the CTS interrupt
NOTE: IER[7:4] can only be modified if EFR[4] is set, i.e., EFR[4] is a write enable.
Re-enabling IER[1] will not cause a new interrupt if the THR is below the
threshold.
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.
BIT SETTINGS
0 = A interrupt is pending
0
1 = No interrupt is pending
3:1
4
3-Bit encoded interrupt. See Table 14.
1 = Xoff/Special character has been detected.
CTS/RTS low to high change of state.
Mirror the contents of FCR[0]
5
7:6
29
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