tms9918

Thank you everybody. Indeed, M1 is available! Just for curiosity, I wrote a program that tests all opcodes (including the undocumented ones) and records the execution on a ‎Z84C0010AEG‎ All the observed patterns are the following [('rd',), ('rd', 'rd'), ('rd', 'rd', 'rd'), ('rd', 'rd', 'rd', 'rd'), ('rd', 'rd', 'rd', 'rd', 'rd'), ('rd', 'rd', 'rd', 'rd', 'rd', 'rd'), ('rd', 'rd', 'rd', 'rd', 'rd', 'wr'), ('rd', 'rd', 'rd', 'rd', 'wr'), ('rd', 'rd', 'rd', 'rd', 'wr', 'wr'), ('rd', 'rd', 'rd', 'wr'), ('rd', 'rd', 'rd', 'wr', 'wr'), ('rd', 'rd', 'wr'), ('rd', 'rd', 'wr', 'wr'), ('rd', 'wr'), ('rd', 'wr', 'wr')] I attach the list of the instructions associated to each pattern for posterity. summary.zip

Yes, I am totally ok with instructions with no writes. I want to be able to stop the system and inspect it,without particular focus on the precise moment I stop it. I just do not want to introduce garbage (i.e. operands with wrong values). I already use emulators extensively, the hardware solution is for inspecting parts of the system which are not documented.

I am trying to develop a debugger that interrupts the program flow by inserting rst instructions on the bus. I want to do it at the beginning of an instruction, i.e. I do not want to modify later parts of multi-byte opcodes / parameters of the opcodes. Unless I solder additional wires (which I'd like to avoid) I have no access to M1. My idea is to detect writes, and replace the data on the bus on the fist read after a write. This holds correct only if there is no instruction that performs a read after a write. If I am not mistaken such instruction does not exist, but I may have overlooked some atypical case. Is there any (possibly undocumented) instruction that performs a memory read after a memory write, or can I be sure that no such instruction exists?