Philips Semiconductors
SC16C554/554D
Quad UART with 16-byte FIFO and infrared (IrDA) encoder/decoder
Product data
Rev. 02 — 13 March 2003
29 of 53
9397 750 11002
Koninklijke Philips Electronics N.V. 2003. All rights reserved.
7.6 Modem Control Register (MCR)
This register controls the interface with the modem or a peripheral device.
Table 18:
Modem Control Register bits description
Bit
Symbol
Description
7
MCR[7]
Reserved; set to 0.
6
MCR[6]
IR enable.
Logic 0 = Enable the standard modem receive and transmit
input/output interface (normal default condition).
Logic 1 = Enable infrared IrDA receive and transmit inputs/outputs.
While in this mode, the TX/RX output/inputs are routed to the
infrared encoder/decoder. The data input and output levels will
conform to the IrDA infrared interface requirement. As such, while
in this mode, the infrared TX output will be a logic 0 during idle data
conditions.
5
MCR[5]
Reserved; set to 0.
4
MCR[4]
Loop-back. Enable the local loop-back mode (diagnostics). In this
mode the transmitter output (TX) and the receiver input (RX), CTS,
DSR, CD, and RI are disconnected from the SC16C554/554D I/O
pins. Internally the modem data and control pins are connected into a
loop-back data conguration (see
Figure 8). In this mode, the receiver
and transmitter interrupts remain fully operational. The Modem
Control Interrupts are also operational, but the interrupts’ sources are
switched to the lower four bits of the Modem Control. Interrupts
continue to be controlled by the IER register.
Logic 0 = Disable loop-back mode (normal default condition).
Logic 1 = Enable local loop-back mode (diagnostics).
3
MCR[3]
OP2, INTx enable. Used to control the modem CD signal in the
loop-back mode.
Logic 0 = Forces INTA-INTD outputs to the 3-State mode during
the 16 mode (normal default condition). In the loop-back mode,
sets OP2 (CD) internally to a logic 1.
Logic 1 = Forces the INTA-INTD outputs to the active mode during
the 16 mode. In the loop-back mode, sets OP2 (CD) internally to a
logic 0.
2
MCR[2]
OP1. This bit is used in the Loop-back mode only. In the loop-back
mode, this bit is used to write the state of the modem RI interface
signal via OP1.
1
MCR[1]
RTS
Logic 0 = Force RTS output to a logic 1 (normal default condition).
Logic 1 = Force RTS output to a logic 0.
Automatic RTS may be used for hardware ow control by enabling
0
MCR[0]
DTR
Logic 0 = Force DTR output to a logic 1 (normal default condition).
Logic 1 = Force DTR output to a logic 0.