HP-71 Diagnostics

[Dave Frederickson]

(06-08-2020 06:50 PM)J-F Garnier Wrote:  The problem with the Diag ROM is that it is a take-over ROM, disabling the internal system ROMs. And moreover, it generates a Module Pulled interrupt as soon as it is inserted, so you can't just have a loop in asm waiting for the insertion (I tried at the time).

The trick is that interrupt is masked IF the CPU is already servicing an interrupt. And there is an easy way: pressing a key generates an interrupt, as long as the CPU is in the keyboard servicing routine, it can't be interrupted again.

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So no logic analyzer?