Modem Control Register (Mcr) - Philips SC16C2550 Manual

Philips Semiconductors

7.6 Modem Control Register (MCR)

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Product data
Dual UART with 16 bytes of transmit and receive FIFOs and IrDA
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.
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
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.
3 MCR[3] OP2/INT enable
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
0 MCR[0] DTR
Rev. 03 — 19 June 2003
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.
Logic 0 = Disable loop-back mode (normal default condition).
Logic 1 = Enable local loop-back mode (diagnostics).
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.
Logic 0 = Force RTS output to a logic 1 (normal default condition).
Logic 1 = Force RTS output to a logic 0.
Logic 0 = Force DTR output to a logic 1 (normal default condition).
Logic 1 = Force DTR output to a logic 0.
SC16C2550
encoder/decoder
Figure 6). In this mode, the receiver
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
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