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SAB-C502-LP

8-Bit CMOS Microcontroller

Infineon Technologies 

C502

Pin Definitions and Functions (cont’d)

Symbol

XTAL1

P2.0 – P2.7

PSEN

*) I = Input

O = Output

Pin Number

P-LCC-44 P-DIP-40

21

19

24–31

21–28

32

29

I/O*) Function

– XTAL1

Input to the inverting oscillator amplifier and

input to the internal clock generator circuits.

To drive the device from an external clock

source, XTAL1 should be driven, while XTAL2

is left unconnected. There are no requirements

on the duty cycle of the external clock signal,

since the input to the internal clocking circuitry

is divided down by a divide-by-two flip-flop.

Minimum and maximum high and low times as

well as rise fall times specified in the AC

characteristics must be observed.

I/O Port 2

ia a bidirectional I/O port with internal pull-up

resistors. Port 2 pins that have 1s written to

them are pulled high by the internal pull-up

resistors, and in that state can be used as

inputs. As inputs, port 2 pins being externally

pulled low will source current (IIL, in the DC

characteristics) because of the internal pull-up

resistors. Port 2 emits the high-order address

byte during fetches from external program

memory and during accesses to external data

memory that use 16-bit addresses (MOVX

@DPTR). In this application it uses strong

internal pull-up resistors when issuing 1s.

During accesses to external data memory that

use 8-bit addresses (MOVX @Ri), port 2

issues the contents of the P2 special function

register.

O The Program Store Enable

output is a control signal that enables the

external program memory to the bus during

external fetch operations. It is activated every

six oscillator periodes except during external

data memory accesses. Remains high during

internal program execution.

Semiconductor Group

9

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