SC16C754 Datasheet, PDF (29/49 Pages) NXP Semiconductors – Quad UART with 64-byte FIFO

Philips Semiconductors
SC16C754
Quad UART with 64-byte FIFO
Table 18: Interrupt priority list
Priority IIR[5] IIR[4] IIR[3]
level
1
0
0
0
2
0
0
1
2
0
0
0
3
0
0
0
4
0
0
0
5
0
1
0
6
1
0
0
IIR[2]
1
1
1
0
0
0
0
IIR[1]
1
0
0
1
0
0
0
IIR[0]
0
0
0
0
0
0
0
Source of the interrupt
Receiver Line Status error
Receiver time-out interrupt
RHR interrupt
THR interrupt
Modem interrupt
Received Xoff signal/
special character
CTS, RTS change of state
from active (LOW) to
inactive (HIGH)
7.10 Enhanced feature register (EFR)
This 8-bit register enables or disables the enhanced features of the UART. Table 19
shows the enhanced feature register bit settings.
Table 19: Enhanced Feature Register bits description
Bit Symbol Description
7
EFR[7] CTS flow control enable.
Logic 0 = CTS flow control is disabled (normal default condition).
Logic 1 = CTS flow control is enabled. Transmission will stop when a
HIGH signal is detected on the CTS pin.
6
EFR[6] RTS flow control enable.
Logic 0 = RTS flow control is disabled (normal default condition).
Logic 1 = RTS flow control is enabled. The RTS pin goes HIGH when
the receiver FIFO HALT trigger level TCR[3:0] is reached, and goes
LOW when the receiver FIFO RESUME transmission trigger level
TCR[7:4] is reached.
5
EFR[5] Special character detect.
Logic 0 = Special character detect disabled (normal default condition).
Logic 1 = Special character detect enabled. 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 a logical 1 to indicate a special
character has been detected.
4
EFR[4] Enhanced functions enable bit.
Logic 0 = Disables enhanced functions and writing to IER[7:4],
FCR[5:4], MCR[7:5].
Logic 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.
3-0 EFR[3:0] Combinations of software flow control can be selected by programming
these bits. See Table 3 “Software flow control options (EFR[0:3])” on
page 10.
9397 750 11618
Product data
Rev. 04 — 19 June 2003
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
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