Datasheet

22
1921D–MICRO–6/08
AT89C55WD
Notes: 1. Write Code Data requires a 200 ns PROG pulse.
2. Write Lock Bits requires a 100 µs PROG pulse.
3. Chip Erase requires a 200 ns - 500 ns PROG pulse.
4. RDY/BSY
signal is output on P3.0 during programming.
Table 21-1. Flash Programming Modes
Mode V
CC
RST PSEN
ALE/
PROG
EA/
V
PP
P2.6 P2.7 P3.3 P3.6 P3.7
P0.7-0
Data
P3.4 P2.5-0 P1.7-0
Address
Write Code
Data
5V H L
(1)
12V L H H H H D
IN
A14 A13-8 A7-0
Read Code
Data
5V H L H H/12V L L L H H D
OUT
A14 A13-8 A7-0
Write Lock Bit
1
6.5
V
HL
(2)
12V H H H H H X X X X
Write Lock Bit
2
6.5
V
HL
(2)
12V H H H L L X X X X
Write Lock Bit
3
6.5
V
HL
(2)
12V H L H H L X X X X
Read Lock Bits
1, 2, 3
5VHL H H HHLHL
P0.2,
P0.3,
P0.4
XX X
Chip Erase
6.5
V
HL
(3)
12V H L H L L X X X X
Read Atmel ID 5V H L H H L L L L L 1EH X XX 0000 00H
Read Device
ID
5V H L H H L L L L L 55H X XX 0001 00H
Read Device
ID
5V H L H H L L L L L 06H X XX 0010 00H