C501 datasheet(11/48 Pages) INFINEON

11 / 48 page

Semiconductor Group

1997-04-01

C501

PSEN

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 periods

except during external data memory

accesses. Remains high during internal

program execution.

RESET

A high level on this pin for two machine

cycles while the oscillator is running

resets the device. An internal diffused

resistor to

SS permits power-on reset

using only an external capacitor to

CC.

ALE/PROG 33

I/O

The Address Latch Enable

output is used for latching the low-byte of

the address into external memory during

normal operation. It is activated every six

oscillator periods except during an

external data memory access.

For the C501-1E this pin is also the

program pulse input (PROG) during OTP

memory programming.

EA/

External Access Enable

When held at high level, instructions are

fetched from the internal ROM (C501-1R

and C501-1E) when the PC is less than

2000H. When held at low level, the C501

fetches all instructions from external

program memory. For the C501-L this

pin must be tied low.

This pin also receives the programming

supply voltage

PP during OTP memory

programming (C501-1E) only).

*) I

= Input

O = Output

Table 1

Pin Deﬁnitions and Functions (cont’d)

Symbol

Pin Number

I/O*) Function

P-LCC-44 P-DIP-40 P-MQFP-44

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