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I have a 65C02S processor wired up and the address and data pins connected to an Arduino Mega so that I can print the state of the data bus and address bus for testing purposes. The 65C02 datasheet states that the RESB input should be held low for 2 clock cycles to initialize the microprocessor and start program execution. As part of the reset, the processor goes through an initialization sequence lasting seven clock cycles. Upon completion of the reset sequence, the program counter is loaded with the reset vector from locations FFFC (low byte) and FFFD (high byte). This is the start location for program control.

I expect to see these two addresses on the address bus after I have advanced the processor through its 7 clock cycles, but I don't see them. My question is: do the data pins (D0-D7) need to supply the processor with an instruction during the reset sequence to ensure that the processor puts the address of the reset vector on the address bus, or is the processor kaput? At the moment, the data pins are connected to the Arduino which is only reading the state of the pins.

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    \$\begingroup\$ I don't think that the CPU needs an instruction during an active reset signal. You might need to look further, if there's anything stopping it from fetching the reset vector, like BE and SYNC. \$\endgroup\$ – the busybee Mar 6 '20 at 8:11
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My question is: do the data pins (D0-D7) need to supply the processor with an instruction during the reset sequence to ensure that the processor puts the address of the reset vector on the address bus

You do not need to drive anything. The processor automatically reads the data from the specified vector location.

is the processor kaput?

Is the processor working fine? is the application running? if yes, processor ist nicht kaput (Processor has not gone bad)

  1. Please check the sampling for a few more samples. is the logging of address data bus fine after or during normal code sequence?
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