C167CS datasheet(129/517 Pages) INFINEON

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C167CS

Derivatives

Parallel Ports

User’s Manual

7-2

V2.0, 2000-07

A write operation to a port pin configured as an input causes the value to be written into

the port output latch, while a read operation returns the latched state of the pin itself. A

read-modify-write operation reads the value of the pin, modifies it, and writes it back to

the output latch.

Writing to a pin configured as an output (DPx.y = ‘1’) causes the output latch and the pin

to have the written value, since the output buffer is enabled. Reading this pin returns the

value of the output latch. A read-modify-write operation reads the value of the output

latch, modifies it, and writes it back to the output latch, thus also modifying the level at

the pin.

7.1

Input Threshold Control

The standard inputs of the C167CS determine the status of input signals according to

TTL levels. In order to accept and recognize noisy signals, CMOS-like input thresholds

can be selected instead of the standard TTL thresholds for all pins of specific ports.

These special thresholds are defined above the TTL thresholds and feature a defined

hysteresis to prevent the inputs from toggling while the respective input signal level is

near the thresholds.

The Port Input Control register PICON allows to select these thresholds for each byte of

the indicated ports, i.e. 8-bit ports are controlled by one bit each while 16-bit ports are

controlled by two bits each.

PICON

Port Input Control Reg.

SFR (F1C4H/E2H)

Reset Value: - - 00H

9876

543210

P8L

P7L

P6L

P4L

P3H

P3L

P2H

P2L

Bit

Function

PxLIN

Port x Low Byte Input Level Selection

Pins Px.7 … Px.0 switch on standard TTL input levels

Pins Px.7 … Px.0 switch on special threshold input levels

PxHIN

Port x High Byte Input Level Selection

Pins Px.15 … Px.8 switch on standard TTL input levels

Pins Px.15 … Px.8 switch on special threshold input levels

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