SC16C652 datasheet(22/41 Pages) PHILIPS

22 / 41 page

Philips Semiconductors

SC16C652

Dual UART with 32 bytes of transmit and receive FIFOs

Product data

Rev. 04 — 20 June 2003

22 of 41

9397 750 11634

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]

Reserved; set to ‘0’.

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 SC16C652 I/O pins.

Internally the modem data and control pins are connected into a

loop-back data conﬁguration (see Figure 4). 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

SC16C652. 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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