HP 16500A, 16510B manual Finding the Answer

Finding the Answer

Your answer is now found in this listing of the states +0000 through +0004.

The 68000 always reads address locations 0, 2, 4, and 6 to find the stack pointer location and memory location for the instruction it fetches after power-up. The 68000 uses two words for each of the locations that it is looking for, a high word and a low word. When the software designer programs the ROM he must put the stack pointer location at address locations 0 and 2. 0 is the high word location and 2 is the low word location. Similarly, the high word of the instruction fetch location must be in address location 4 and the low word in location 6.

Since the software design calls for the reset vector to:

1.Set the stack pointer to be set to 04FC,

2.Read memory address location 8048 for its first instruction fetch,

you are interested in what is on both the address bus and the data bus in states 0 through 3.

You look at the following listing and see that states 0 and 1 do contain address locations 0 and 2 under the ADDR label, indicating the microprocessor did look to the correct locations for the stack pointer data. You also see that the data contained in these ROM locations are 0000 and 04FC, which are correct.

You then look at states 2 and 3. You see that the next two address locations are 4 and 6, which is correct, and the data found at these locations is 0000 and 8048, which is also correct.

Using the State Analyzer	HP 16510B
8 - 20	Front-Panel Reference