Philips Semiconductors Product data
P87C554
80C51 8-bit microcontroller – 12 clock operation
16K/512 OTP/RAM, 8 channel 10-bit A/D, I
2
C, PWM,
capture/compare, high I/O
2002 Mar 25
72
EPROM CHARACTERISTICS
The 87C554 contains three signature bytes that can be read and
used by an EPROM programming system to identify the device. The
signature bytes identify the device as an 87C554 manufactured by
Philips:
(030H) = 15H indicates manufactured by Philips Components
(031H) = 93H indicates 87C554
(60H) = 01H
Program Verification
If security bits 2 or 3 have not been programmed, the on-chip
program memory can be read out for program verification.
If the encryption table has been programmed, the data presented at
port 0 will be the exclusive NOR of the program byte with one of the
encryption bytes. The user will have to know the encryption table
contents in order to correctly decode the verification data. The
encryption table itself cannot be read out.
Security Bits
With none of the security bits programmed the code in the program
memory can be verified. If the encryption table is programmed, the
code will be encrypted when verified. When only security bit 1 (see
Table 11) is programmed, MOVC instructions executed from external
program memory are disabled from fetching code bytes from the
internal memory, EA
is latched on Reset and all further programming
of the EPROM is disabled. When security bits 1 and 2 are
programmed, in addition to the above, verify mode is disabled.
When all three security bits are programmed, all of the conditions
above apply and all external program memory execution is disabled.
Table 11. Program Security Bits for EPROM Devices
PROGRAM LOCK BITS
1,
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.
NOTES:
1. P – programmed. U – unprogrammed.
2. Any other combination of the security bits is not defined.
