IS89C51 Datasheet, PDF (36/48 Pages) Integrated Silicon Solution, Inc – CMOS SINGLE CHIP 8-BIT MICROCONTROLLER with 4-Kbytes of FLASH

IS89C51
Program Memory Lock System
The program lock system, when programmed, protects
the code against software piracy. The IS89C51 has a
three-level program lock system (see Table 12). The lock-
bits are programmed in the same manner as the program
memory.
The detailed lock-bits features are listed in Table 12.
ISSI ^®
Table 12. Program Lock Bits
LB1
LB2
LB3
1
U
U
U
2
P
U
U
3
P
P
U
4
P
P
P
Protection Type
No Program Lock Features enabled.
MOVC instructions executed from external program memory are diabled
form fetching code bytes from internal memory, EA is sampled and
latched on Reset and further programming of the Flash is disabled.
Same as 2, also verify is disabled.
Same as 3, also external execution is disabled.
FLASH MEMORY
Programming the IS89C51
The IS89C51 is normally shipped with the on-chip Flash
memory array in the erased state (i.e., contents = FFH)
and ready to be programmed. The IS89C51 is programmed
byte-by-byte in programming mode. Before the on-chip
flash code memory can be re-programmed, the entire
memory array must be erased electrically.
Programming Interface
Every code byte in the Flash array can be written and the
entire array can be erased using the appropriate
combination of control signals. The write operation cycles
is self-timed once initiated, will automatically time itself to
completion. The programming interface is shown in
Table 13 and Figures 24 and 25.
Table 13. Flash Programming Mode
Mode
RST PSEN
Program Code Data
H
L
Verify Code Data
H
L
Program Lock Bit 1
H
L
Program Lock Bit 2
H
L
Program Lock Bit 3
H
L
Read Signature Byte H
L
Chip Erase
H
L
ALE/PROG
H
H
EA/VPP
12V
H
12V
12V
12V
H
12V
P2.6
L
L
H
H
H
L
H
P2.7
H
L
H
H
L
L
L
P3.6
H
H
H
L
H
L
L
P3.7
H
H
H
L
L
L
L
36
1-800-379-4774 — Integrated Silicon Solution, Inc.
MC016-1C
11/21/98