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¡ Semiconductor

MSM82C51A-2RS/GS/JS

TXRDY (output terminal)

This is an output terminal which indicates that the MSM82C51A-2 is ready to accept a

transmitted data character. But the terminal is always at low level if CTS = high or the device

was set in “TX disable status” by a command.

Note:

TXRDY status word indicates that transmit data character is receivable,

regardless

of CTS or command.

If the CPU writes a data character, TXRDY will be reset by the leading edge or WR

signal.

TXEMPTY (Output terminal)

This is an output terminal which indicates that the MSM82C51A-2 has transmitted all the

characters and had no data character.

In “synchronous mode,” the terminal is at high level, if transmit data characters are no longer

remaining and sync characters are automatically transmitted. If the CPU writes a data

character, TXEMPTY will be reset by the leading edge of WR signal.

Note : As the transmitter is disabled by setting CTS “High” or command, data written

before disable will be sent out. Then TXD and TXEMPTY will be “High”.

Even if a data is written after disable, that data is not sent out and TXE will be

“High”.After

the transmitter is enabled, it sent out. (Refer to Timing Chart of

Transmitter Control and Flag

Timing)

TXC (Input terminal)

This is a clock input signal which determines the transfer speed of transmitted data.

In “synchronous mode,” the baud rate will be the same as the frequency of TXC.

In “asynchronous mode”, it is possible to select the baud rate factor by mode instruction.

It can be 1, 1/16 or 1/64 the TXC.

The falling edge of TXC sifts the serial data out of the MSM82C51A-2.

RXD (input terminal)

This is a terminal which receives serial data.

RXRDY (Output terminal)

This is a terminal which indicates that the MSM82C51A-2 contains a character that is ready to

READ.

If the CPU reads a data character, RXRDY will be reset by the leading edge of RD signal.

Unless the CPU reads a data character before the next one is received completely, the preceding

data will be lost. In such a case, an overrun error flag status word will be set.

RXC (Input terminal)

This is a clock input signal which determines the transfer speed of received data.

In “synchronous mode,” the baud rate is the same as the frequency of RXC.

In “asynchronous mode,” it is possible to select the baud rate factor by mode instruction.

It can be 1, 1/16, 1/64 the RXC.