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14-1

CHAPTER 14

PROGRAMMING AND VERIFYING

NONVOLATILE MEMORY

This chapter provides instructions for programming and verifying on-chip nonvolatile memory

on the 8XC251Sx. The programming instructions cover the entry of program code into on-chip

code memory, configuration information into the on-chip configuration bytes, and other catego-

ries of information into on-chip memory outside the memory address space. The verify instruc-

tions permit reading these memory locations to verify their contents. The operations covered in

this chapter are:

• programming and verifying the on-chip code memory (8 Kbytes, 16 Kbytes)

• programming and verifying the on-chip configuration bytes (8 bytes)

• programming and verifying the lock bits (3 bits)

• programming the encryption array (128 bytes)

• verifying the signature bytes (3 bytes)

Programming instructions apply to the 87C251Sx (one-time programmable ROM (OTPROM)

and erasable programmable ROM (EPROM)). Verify instructions apply to the 87C251Sx, the

83C251Sx (mask ROM), and the configuration bytes on the 80C251SB, SQ (no ROM/OTPROM/

EPROM). In the unprogrammed state, EPROM and OTPROM contains all 1s.

14.1 GENERAL

The 87C251Sx is programmed and verified in the same manner as the 87C51FX, using the same

quick-pulse programming algorithm, which programs at V

= 12.75 V using a series of five

100-µs PROG# pulses per byte. This results in a programming time of approximately 16 seconds

for the 16-Kbyte on-chip code memory.

Programming and verifying operations differ from normal microcontroller operation. Memory

accesses are made one byte at a time, input/output ports are used in a different manner, and the

EA#/V

and ALE/PROG# pins are used for their alternative (programming) functions. For a

complete list of signal descriptions, see Appendix B.

Intel 8XC251SA User Manual

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