8XC196Kx, Jx, CA USER’S MANUAL

16.8.4 Slave Programming Routines

The slave programming mode algorithm consists of three routines: the address/command decoding routine, the program word routine, and the dump word routine.

The address/command decoding routine (Figure 16-7) reads the PBUS and transfers control to the program word or dump word routine based on the value of P3.0. A one on P3.0 selects the program word command and the remaining bits specify the address. For example, a PBUS value of 3501H programs a word of data at location 3500H. A zero on P3.0 selects the dump word command and the remaining bits specify the address. For example, a PBUS value of 3500H places the word at location 3500H on the PBUS.

The program word routine (Figure 16-8) checks the CCB security-lock bits. If either security lock bit (CCB0.6 or CCB0.7) has been programmed, you must provide a matching security key to gain access to the device. Using the program word command, write eight consecutive words to the device, starting at location 2020H and continuing to 202FH. The routine stores these eight words in an internal register and compares their value with the internal key. If the keys match, the routine allows you to program individual or sequential OTPROM locations; otherwise, the device enters an endless loop.

The dump word routine (Figure 16-10) also checks the CCB security-lock bits, but it has no provision for security key verification. If the lock bits are unprogrammed, the routine fetches a word of data from the OTPROM and writes that data to the PBUS. If either lock bit is programmed, the routine performs a write cycle without first getting data from the OTPROM.

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From Address/

Command Decoder

A0194-03

Figure 16-8. Program Word Routine

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PROGRAMMING THE NONVOLATILE MEMORY

Figure 16-9 shows the timings of the program word command with a repeated programming pulse and auto increment. Asserting PALE# latches the command and address on the PBUS. Asserting PROG# latches the data on the PBUS and starts the programming sequence. The PROG# signal controls the programming pulse width. (Slave programming mode does not use the PPW.) After the rising edge of PROG#, the routine verifies the contents of the location that was just programmed and asserts PVER to indicate successful programming. AINC# is optional and can automatically increment the address for the next location. If you do not use AINC#, you must send a new program word command to access the next word location.

*Additional program pulses and verifications.

**Measure from falling edge of last PROG# pulse in sequence.

A0121-01

Figure 16-9. Program Word Waveform

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A0189-03

Figure 16-10. Dump Word Routine

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