Z80 datasheet(264/330 Pages) ZILOG

264 / 330 page

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7UGT /CPWCN

UM008101-0601

Serial Input/Output

244

Synchronous Transmit

Initialization

The system program must initialize the transmitter with the following

parameters: odd or even parity, x1 clock mode, 8-bit or 16-bit sync char-

acter(s), CRC polynomial, Transmitter Enables, Request To Send, Data

Terminal Ready, interrupt modes, and transmit character length. WR4

parameters must be issued before WR1, WR3, WR5, WR6, and WR7

parameters or commands.

One of two polynomials, CRC -16(X16 +X15 +X2 + 1)orSDLC(X16 +

X12 +X5 + 1), may be used with synchronous modes. In either case (SDLC

mode not selected), the CRC generator and checker are reset to all 0s. In the

transmit initialization process, the CRC generator is initialized by setting

the Reset Transmit CRC Generator command bits (WR0). Both the trans-

mitter and the receiver use the same polynomial.

Transmit Interrupt Enable or Wait/Ready Enable can be selected to transfer

the data. The External/Status interrupt mode is used to monitor the status of

the CLEAR TO SEND (CTS) input as well as the Transmit Underrun/EOM

latch. Optionally, the Auto Enables feature can be used to enable the trans-

mitter when CTS is active. The first data transfer to the Z80 SIO can begin

when the External/Status interrupt occurs (CTS status bit set) or immediately

following the Transmit Enable command (if the Auto Enables modes is set).

Transmit data is held marking after reset or if the transmitter is not

enabled. Break may be programmed to generate a spacing line that begins

as soon as the Send Break bit is set. With the transmitter fully initialized

and enabled, the default condition is continuous transmission of the 8-bit

or 16-bit sync character.

Data Transfer and Status Monitoring

Z80 Datasheet(PDF) 264 Page - Zilog, Inc.