M68SDIL datasheet(54/432 Pages) MOTOROLA

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Pinout and Signal Descriptions

Advance Information

68HC(9)12D60 — Rev 4.0

Pinout and Signal Descriptions

MOTOROLA

3.6.2 Port B

Port B pins are used for address and data in expanded modes. In single

chip modes, the pins can be used as I/O. The port data register is not in

the address map during expanded and peripheral mode operation.

When it is in the map, port B can be read or written at anytime.

DDRB is not in the address map during expanded and peripheral mode

operation. Setting a bit in DDRB makes the corresponding bit in port B

an output; clearing a bit in DDRB makes the corresponding bit in port B

an input. The default reset state of DDRB is all zeros.

When the PUPB bit in the PUCR register is set, all port B input pins are

pulled-up internally by an active pull-up device. This bit has no effect if

the port is being used in expanded modes as the pull-ups are inactive.

Setting the RDPB bit in register RDRIV causes all port B outputs to have

reduced drive level. RDRIV can be written once after reset. RDRIV is not

in the address map in peripheral mode. Refer to Bus Control and

Input/Output.

3.6.3 Port E

Port E pins operate differently from port A and B pins. Port E pins are

used for bus control signals and interrupt service request signals. When

a pin is not used for one of these specific functions, it can be used as

general-purpose I/O. However, two of the pins (PE[1:0]) can only be

used for input, and the states of these pins can be read in the port data

The PEAR register determines pin function, and register DDRE

determines whether each pin is an input or output when it is used for

general-purpose I/O. PEAR settings override DDRE settings. Because

PE[1:0] are input-only pins, only DDRE[7:2] have effect. Setting a bit in

the DDRE register makes the corresponding bit in port E an output;

clearing a bit in the DDRE register makes the corresponding bit in port E

an input. The default reset state of DDRE is all zeros.

Freescale Semiconductor, Inc.

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M68SDIL Datasheet(PDF) 54 Page - Motorola, Inc