87C654 Philips Semiconductors, 87C654 Datasheet - Page 16

• Manufacturer Part Number: 87C654
• Description: 80C51 8-bit microcontroller 8K/16K/ 256 OTP/ I2C
• Manufacturer: Philips Semiconductors

Philips Semiconductors
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
1996 Aug 16
PORT 0
PORT 2
CMOS single-chip 8-bit microcontroller
PSEN
ALE
RD
PORT 0
PORT 2
PSEN
ALE
t
AVLL
FROM RI OR DPL
A0–A7
t
LLAX
t
t
AVWL
LHLL
t
t
LLWL
AVLL
A0–A7
t
Figure 1. External Program Memory Read Cycle
t
P2.0–P2.7 OR A8–A15 FROM DPH
AVDV
RLAZ
t
Figure 2. External Data Memory Read Cycle
LLDV
Q – Output data
R – RD signal
t – Time
V – Valid
W – WR signal
X – No longer a valid logic level
Z – Float
Examples: t
t
t
t
AVIV
LLAX
LLPL
t
LLIV
t
t
PLIV
RLDV
A0–A15
t
t
PLAZ
AVLL
LLPL
t
PLPH
t
RLRH
t
= Time for address valid
= Time for ALE low
PXIX
to ALE low.
to PSEN low.
INSTR IN
16
t
RHDX
DATA IN
t
PXIZ
t
RHDZ
t
WHLH
A0–A7
A0–A7 FROM PCL
A8–A15 FROM PCH
A8–A15
Product specification
87C654
INSTR IN
SU00006
SU00177