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Posted By

TLC
on 2011-02-09
08:29:25
 Re: cartridge programming

IMHO there's no way to coldboot a Plus/4 from an external cartridge, unless the machine is modified.

If you check the schematics (http://zimmers.net/anonftp/pub/cbm/schematics/computers/plus4/plus4-310164-4of4.gif) closely, you can deduct that ROM config (the active ROM configuration) is stored by U21, 74LS175. This 4x flip-flop is cleared by RESET'. Consequently, whenever reset happens (either power-on reset or the reset button is activated), bank 0 will be active (which is BASIC + KERNAL). So you'll have to follow the standard ROM boot process (as described by siz ), or you'll need to invent some way to hijack it.



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