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80C51 Datasheet, PDF (30/38 Pages) NXP Semiconductors – 80C51 8-bit microcontroller family 4K/128 OTP/ROM/ROMless low voltage 2.7V.5.5V, low power, high speed 33 MHz
Philips Semiconductors
80C51 8-bit microcontroller family
4K/128 OTP/ROM/ROMless, low voltage (2.7V–5.5V),
low power, high speed (33 MHz)
Product specification
80C51/87C51/80C31
Table 8. EPROM Programming Modes
MODE
Read signature
RST
1
PSEN
0
ALE/PROG
1
EA/VPP
1
P2.7
0
P2.6
0
P3.7
0
P3.6
0
Program code data
Verify code data
1
0
1
0
0*
VPP
1
0
1
1
1
1
0
0
1
1
Pgm encryption table
1
0
0*
VPP
1
0
1
0
Pgm security bit 1
1
0
0*
VPP
1
1
1
1
Pgm security bit 2
1
0
0*
VPP
1
1
0
0
Pgm security bit 3
1
0
0*
VPP
0
1
0
1
NOTES:
1. ‘0’ = Valid low for that pin, ‘1’ = valid high for that pin.
2. VPP = 12.75V ±0.25V.
3. VCC = 5V±10% during programming and verification.
* ALE/PROG receives 5 programming pulses for code data (also for user array; 5 pulses for encryption or security bits) while VPP is held at
12.75V. Each programming pulse is low for 100µs (±10µs) and high for a minimum of 10µs.
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.
2000 Jan 20
30