Philips Semiconductors
80C51 8-bit microcontroller family
4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V),
low power, high speed (30/33 MHz)
Preliminary data
80C3xX2; 80C5xX2;
87C5xX2
Table 9. Program Security Bits for EPROM Devices
PROGRAM LOCK BITS1, 2
SB1 SB2 SB3 PROTECTION DESCRIPTION
1
U
U
U No Program Security features enabled. (Code verify will still be encrypted by the Encryption Array if
programmed.)
2
P
U
U MOVC instructions executed from external program memory are disabled from fetching code bytes
from internal memory, EA is sampled and latched on Reset, and further programming of the EPROM
is disabled.
3
P
P
U Same as 2, also verify is disabled.
4
P
P
P Same as 3, external execution is disabled. Internal data RAM is not accessible.
NOTES:
1. P – programmed. U – unprogrammed.
2. Any other combination of the security bits is not defined.
+5V
A0–A7
1
1
1
4–6MHz
P1
RST
P3.6
P3.7
XTAL2
XTAL1
VSS
VCC
P0
OTP
EA/VPP
ALE/PROG
PSEN
P2.7
P2.6
P2.0–P2.5
Figure 40. Programming Configuration
PGM DATA
+12.75V
5 PULSES TO GROUND
0
1
0
A8–A12
SU01488
5 PULSES
1
ALE/PROG:
0
1
2
3
4
5
SEE EXPLODED VIEW BELOW
1
ALE/PROG:
0
tGLGH = 100µs±10µs
tGHGL = 10µs MIN
1
Figure 41. PROG Waveform
SU00875
2001 Sep 24
47