
Philips Semiconductors
Product specification
80C51/87C51/80C31
80C51 8-bit microcontroller family
4K/128 OTP/ROM/ROMless, low voltage (2.7V–5.5V),
low power, high speed (33 MHz)
2000 Jan 20
26
t
LLAX
ALE
PSEN
PORT 0
PORT 2
WR
A0–A7
FROM RI OR DPL
DATA OUT
A0–A7 FROM PCL
INSTR IN
P2.0–P2.7 OR A8–A15 FROM DPF
A0–A15 FROM PCH
t
WHLH
t
LLWL
t
WLWH
t
AVLL
t
AVWL
t
QVWX
t
WHQX
t
QVWH
SU00026
Figure 16. External Data Memory Write Cycle
0
1
2
3
4
5
6
7
8
INSTRUCTION
ALE
CLOCK
OUTPUT DATA
WRITE TO SBUF
INPUT DATA
CLEAR RI
VALID
VALID
VALID
VALID
VALID
VALID
VALID
VALID
SET TI
SET RI
t
XLXL
t
QVXH
t
XHQX
t
XHDX
t
XHDV
SU00027
1
2
3
0
4
5
6
7
Figure 17. Shift Register Mode Timing
V
CC
–0.5
0.45V
0.7V
CC
0.2V
CC
–0.1
t
CHCL
t
CLCL
t
CLCH
t
CLCX
t
CHCX
SU00009
Figure 18. External Clock Drive