TS68230 datasheet(30/61 Pages) STMICROELECTRONICS

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PBCR

5 4 3

H4 Control

0 X X

Input pin - edge-sensitive status input, H4S is set on an asserted edge.

1 0 0

Output pin - negated, H4S is always cleared.

1 0 1

Output pin - asserted, H4S is always cleared.

1 1 0

Output pin - interlocked input handshake protocol.

1 1 1

Output pin - pulsed input handshake protocol.

PBCR

H4 Interrupt Enable

The H4 interrupt is disabled.

The H4 interrupt is enabled.

PBCR

H3 SVCRQ Enable

The H3 interrupt and DMA request are disabled.

The H3 interrupt and DMA request are enabled.

PBCR

H3 Status Control

The H3S status bit is set when either the initial or final output latch of ports A and B can accept

new data. It is clear when both latches are full and cannot accept new data.

The H3S status bit is set when both the initial and final output latches of ports A and B are empty.

The H3S status bit is clear when at least one set of output latches is full.

3.5. MODE 2 - BIDIRECTIONAL 8-BIT MODE

In mode 2, port A is used for bit I/O with no associa-

ted handshake pins. Port B is used for bidirectional

8-bit double-buffered transfers. H1 and H2, enabled

by the H12 enable bit in the port general control re-

gister, control output transfers, while H3 and H4,

enabled by the port general control register bit H34

enable, control input transfers. The instantaneous

direction of the data is determined by the H1 hand-

shake pin. The port B data direction register is not

used. The port A and port B submode fields do not

affect PI/T operation in mode 2.

3.5.1. PORT A BIT I/O (PIN-DEFINABLE SINGLE-

BUFFERED OUTPUT OR NON-LATCHED IN-

PUT). Mode 2, port A performs simple bit I/O with no

associated handshake pins. This configuration is in-

tended for applications in which several inde-

pendent devices must be controlled or monitored.

Data written to the port A data register is single buf-

fered. If the port A data direction register bit for that

pin is set (output), the output buffer is enabled. If it

is zero (input), data written is still latched but not

available at the pin. Data read from the data register

is either the instantaneous value of the pin (if data

is stable from CS asserted to DTACK asserted, data

on these pins will be guaranteed valid in the data re-

gister) or what was written to the data register, de-

pending on the contents of the port A data direction

Programmable Options Mode 1 - Port A Submode XX and Port B Submode X1 (continued)

TS68230

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