C167CS datasheet(171/517 Pages) INFINEON

171 / 517 page

C167CS

Derivatives

Parallel Ports

User’s Manual

7-44

V2.0, 2000-07

Figure 7-21

Port 6 IO and Alternate Functions

The chip select lines of Port 6 additionally have an internal weak pullup device. This

device is switched on under the following conditions:

• always during reset for all potential CS output pins

• if the Port 6 line is used as a chip select output,

and the C167CS is in Hold mode (invoked through HOLD),

and the respective pin driver is in push/pull mode (ODP6.x = ‘0’).

This feature is implemented to drive the chip select lines high during reset in order to

avoid multiple chip selection, and to allow another master to access the external memory

via the same chip select lines (Wired-AND), while the C167CS is in Hold mode.

With ODP6.x = ‘1’ (open drain output selected), the internal pullup device will not be

active during Hold mode; external pullup devices must be used in this case.

When entering Hold mode the CS lines are actively driven high for one clock phase, then

the output level is controlled by the pullup devices (if activated).

After reset the CS function must be used, if selected so. In this case there is no possibility

to program any port latches before. Thus the alternate function (CS) is selected

automatically in this case.

Note: The open drain output option can only be selected via software earliest during the

initialization routine; the configured chip select lines (via CSSEL) will be in push/

pull output driver mode directly after reset.

MCA04358

P6.7

P6.6

P6.5

P6.4

P6.3

P6.2

P6.1

P6.0

Port 6

Alternate Function

General Purpose

Input/Output

BREQ

HLDA

HOLD

CS4

CS3

CS2

CS1

CS0

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