68HC705SP7 datasheet(90/230 Pages) FREESCALE

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Parallel Input/Output

General Release Specification

MC68HC705JJ7/MC68HC705JP7 — Rev. 3.0

Parallel Input/Output

When using the PB4/AN4/TCMP/CMP1 pin, the following interactions

must be noted:

1. If the OLVL timer output compare function is the required output

function, then the DDRB4 bit must be set, the PB4 data bit must

be cleared and the OPT bit in the MOR must be cleared. The

PB4/AN4/TCMP/CMP1 pin becomes an output which follows the

state of the OLVL bit. The pulldown device will be disabled in this

case. The analog subsystem would not normally use this pin as an

analog input in this case.

2. If the PB4 data bit is the required output function, then the DDRB4

bit must be set, the OLVL bit in the TCR must be cleared and the

OPT bit in the MOR must be cleared. The pulldown device will be

disabled in this case. The analog subsystem would not normally

use this pin as an analog input in this case.

3. If the comparator 1 output is the desired output function then the

PB4 data bit must be cleared, the DDRB4 bit must be set, the

OLVL bit in the TCR must be cleared and the OPT bit in the MOR

must be set. The PB4/AN4/TCMP/CMP1 pin becomes an output

which follows the state of the OLVL bit. The pulldown device will

be disabled in this case. The analog subsystem would not

normally use this pin as an analog input in this case.

4. If the PB4 pin is to be an input to the analog subsystem or a digital

input, then the DDRB4 bit must be cleared. In this case, the PB4

pin can still be read; but the voltage present will be returned as a

binary value. Depending on the external application, the PB4

pulldown may also be disabled by setting the PDIB4 pulldown

inhibit bit. In this case both the digital and analog functions

connected to this pin can be utilized.

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