TUSB5052 datasheet(53/82 Pages) TI

53 / 82 page

7−5

7.1.5

MCR[2:1]: Modem-Control Registers (2 Registers)

These registers provide control for modem interface I/O, and definition of the flow control mode.

LCD

LRI

RTS

RTR

SEN

LOOP

RCVE

URST

R/W

BIT

NAME

RESET

FUNCTION

URST

UART soft reset. This bit can be used by the MCU to reset the UART.

URST

URST = 0

Normal operation. Writing a 0 by MCU has no effect.

URST = 1

When the MCU writes a 1 to this bit, a UART reset is generated (ORed with hard reset). When the

UART exits the reset state, URST is cleared. The MCU can monitor this bit to determine if the UART

completed the reset cycle.

RCVE

Receiver enable bit. This bit is valid only when 485E in FCRL is 1 (RS485 mode). When 485E = 0, this bit has no

effect on the receiver.

RCVE = 0

When 485E = 1, the UART receiver is disabled if RTS and DTR are active. (When data are

transmitted the UART-receiver is disabled.)

RCVE = 1

When 485 = 1, the UART receiver is enabled regardless of the RTS/DTR state (UART receiver is on

all the time).

LOOP

This bit controls the normal/loop-back mode of operation (see Figure 7−1).

LOOP

LOOP = 0

Normal operation

LOOP = 1

Enable loop-back mode of operation. In this mode the following occurs:

• SOUT is set high.

• SIN is disconnected.

• The transmitter is looped back into the receiver.

• The four modem-control inputs, CTS, DSR, DCD, and RI are disconnected.

• DTR, RTS, LRI and LCD are internally connected to the four modem-control inputs, and read in the

MSR register as follows:

• DTR is reflected in MSR[4] bit.

• RTS is reflected in MSR[5] bit.

• LRI is reflected in MSR[6] bit.

• LCD is reflected in MSR[7] bit.

RSV

Reserved = 0

DTR

This bit controls the state of the DTR output pin (see Figure 7−1). This bit has no effect when auto-flow control is

used.

DTR = 0 Forces the DTR output pin to inactive (high)

DTR = 1 Forces the DTR output pin to active (low)

RTS

This bit controls the state of the RTS output pin (see Figure 7−1). This bit has no effect when auto-flow control is

used.

RTS = 0 Forces the RTS output pin to inactive (high)

RTS = 1 Forces the RTS output pin to active (low)

LRI

This bit is used for loopback mode only. When in loopback mode, this bit is reflected in MSR[6]-bit (see Figure 7−1).

LRI = 0 Clears MSR[6] = 0

LRI = 1 Sets MSR[6] = 1

LCD

This bit is used for loopback mode only. When in loopback mode, this bit is reflected in MSR[7]-bit (see Figure 7−1).

LCD = 0

Clears MSR[7] = 0

LCD = 1

Sets MSR[7] = 1

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