SC16C652B datasheet(23/44 Pages) PHILIPS

23 / 44 page

Philips Semiconductors

SC16C652B

Dual UART with 32-byte FIFOs and IrDA encoder/decoder

Product data

Rev. 03 — 10 December 2004

23 of 44

9397 750 14452

7.6 Modem Control Register (MCR)

This register controls the interface with the modem or a peripheral device.

Table 20:

Modem Control Register bits description

Bit

Symbol

Description

MCR[7]

Clock select

Logic 0 = Divide by 1 clock input.

Logic 1 = Divide by 4 clock input.

MCR[6]

IR enable (see Figure 17).

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.

MCR[5]

Reserved; set to ‘0’.

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 SC16C652B I/O pins.

Internally the modem data and control pins are connected into a

loop-back data conﬁguration (see Figure 5). 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).

MCR[3]

OP2/INT enable

Logic0=Forces INT (A-B) outputs to the 3-State mode and sets

OP2 to a logic 1 (normal default condition).

Logic1=Forces the INT (A-B outputs to the active mode and sets

OP2 to a logic 0.

MCR[2]

(OP1). OP1A/OP1B are not available as an external signal in the

SC16C652B. 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.

MCR[1]

RTS

Logic 0 = Force RTS output to a logic 1 (normal default condition).

Logic1=Force RTS output to a logic 0.

MCR[0]

DTR

Logic 0 = Force DTR output to a logic 1 (normal default condition).

Logic1=Force DTR output to a logic 0.

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