2001 Apr 06

23

Philips Semiconductors

Preliminary specification

P87C51MB2/P87C51MC2

80C51 8-bit microcontroller family with extended memory

64KB/96KB OTP with 2KB/3KB RAM

EXPLANATION OF AC SYMBOLS

Each timing symbol has five characters. The first character is always ‘t’ (= time). The other characters, depending on their

positions, indicate the name of a signal or the logical status of that signal. The designations are:

A – Address

C – Clock

D – Input data

H – Logic level high

I – Instruction (program memory contents)

L – Logic level low, or ALE

P – PSEN

Q – Output data

R – RD signal

t – Time

V – Valid

W– WR signal

X – No longer a valid logic level

Z – Float

Examples:

Figure 1: External Program Memory Read Cycle (Non-Extended Memory Cycle)

ALE

PSEN

PORT 0

PORT 2

A0-A7

INSTR IN

P2.0-P2.7 OR A8-A15

A0-A7