Philips Semiconductors

Product specification

OM5232

CMOS single-chip 8-bit microcontroller

December 1994

9

EXPLANATION OF THE 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

to ALE low.

to PSEN low.

Figure 2. External Program Memory Read Cycle

ALE

PSEN

PORT 0

PORT 2

A8–A15

A8–A15

A0–A7

A0–A7

INSTR IN

ALE

PSEN

PORT 0

PORT 2

Figure 3. External Data Memory Read Cycle

RD

A0–A7

FROM RI OR DPL

DATA IN

A0–A7 FROM PCL

INSTR IN

P2.0–P2.7 OR A8–A15 FROM DPH

A8–A15 FROM PCH