Philips Semiconductors

Product specification

80C51/87C51/80C31

80C51 8-bit microcontroller family

4K/128 OTP/ROM/ROMless, low voltage (2.7V–5.5V),

low power, high speed (33 MHz)

2000 Jan 20

33

MASK ROM DEVICES

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 10) 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.

Encryption Array

64 bytes of encryption array are initially unprogrammed (all 1s).

Table 10. Program Security Bits

SB1

SB2

PROTECTION DESCRIPTION

1

U

U

No Program Security features enabled.

(Code verify will still be encrypted by the Encryption Array if programmed.)

2

P

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.

NOTES:

1. P – programmed. U – unprogrammed.

2. Any other combination of the security bits is not defined.

ROM CODE SUBMISSION

When submitting ROM code for the 80C51, the following must be specified:

1. 4k byte user ROM data

2. 64 byte ROM encryption key

3. ROM security bits.

ADDRESS

CONTENT

BIT(S)

COMMENT

0000H to 0FFFH

DATA

7:0

User ROM Data

1000H to 103FH

KEY

7:0

ROM Encryption Key

1040H

SEC

0

ROM Security Bit 1

1040H

SEC

1

ROM Security Bit 2

Security Bit 1:

When programmed, this bit has two effects on masked ROM parts:

1. External MOVC is disabled, and

2. EA is latched on Reset.

Security Bit 2:

When programmed, this bit inhibits Verify User ROM.

NOTE: Security Bit 2 cannot be enabled unless Security Bit 1 is enabled.

If the ROM Code file does not include the options, the following information must be included with the ROM code.

For each of the following, check the appropriate box, and send to Philips along with the code:

Security Bit #1:

Security Bit #2:

Encryption:

If Yes, must send key file.