Datasheet

TL16C752B-EP

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SGLS153B –FEBRUARY 2003–REVISED DECEMBER 2007

Modem Status Register (MSR)

The modem status register is an 8-bit register that provides information about the current state of the control

lines from the modem, data set, or peripheral device to the processor. It also indicates when a control input from

the modem changes state. Table 13 shows the modem status register bit settings per channel.

Table 13. Modem Status Register (MSR) Bit Settings

BIT NO. BIT SETTINGS

0 Indicates that the CTS input (or MCR[1] in loopback) has changed state. Cleared on a read.

1 Indicates that the DSR input (or MCR[0] in loopback) has changed state. Cleared on a read.

2 Indicates that the RI input (or MCR[2] in loopback) has changed state from low to high. Cleared on a read.

3 Indicates that the CD input (or MCR[3] in loopback) has changed state. Cleared on a read.

4 This bit is the complement of the CTS input during normal mode. During internal loopback mode, it is equivalent to

MCR[1].

5 This bit is the complement of the DSR input during normal mode. During internal loopback mode, it is equivalent to

MCR[0].

6 This bit is the complement of the RI input during normal mode. During internal loopback mode, it is equivalent to MCR[2].

7 This bit is the complement of the CD input during normal mode. During internal loopback mode, it is equivalent to MCR[3].

Interrupt Enable Register (IER)

The interrupt enable register (IER) enables each of the six types of interrupt, receiver error, RHR interrupt, THR

interrupt, Xoff received, or CTS/RTS change of state from low-to-high. The INT output signal is activated in

response to interrupt generation. Table 14 shows the IER bit settings.

Table 14. Interrupt Enable Register (IER) Bit Settings

BIT NO. BIT SETTINGS

0 0 = Disable the RHR interrupt

1 = Enable the RHR interrupt

1 0 = Disable the THR interrupt

1 = Enable the THR interrupt

2 0 = Disable the receiver line status interrupt

1 = Enable the receiver line status interrupt

3 0 = Disable the modem status register interrupt

1 = Enable the modem status register interrupt

4 0 = Disable sleep mode

1 = Enable sleep mode

5 0 = Disable the Xoff interrupt

1 = Enable the Xoff interrupt

6 0 = Disable the RTS interrupt

1 = Enable the RTS interrupt

7 0 = Disable the CTS interrupt

1 = Enable the CTS interrupt

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