Philips Semiconductors
SC16C2550
Dual UART with 16 bytes of transmit and receive FIFOs and IrDA
encoder/decoder
Product data
Rev. 03 — 19 June 2003
24 of 46
9397 750 11621
© 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 17:
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 SC16C2550 I/O pins.
Internally the modem data and control pins are connected into a
loop-back data configuration (see
). 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/INT enable
Logic 0 = Forces INT (A-B) outputs to the 3-State mode and sets
OP2 to a logic 1 (normal default condition).
Logic 1 = Forces the INT (A-B outputs to the active mode and sets
OP2 to a logic 0.
2
MCR[2]
(OP1). OP1A/OP1B are not available as an external signal in the
SC16C2550. This bit is instead 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.
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.
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.