Initial inspection of pin 8 on u38 gives me 5.5v when bank 2 is selected and 3.5v when bank 1 is selected. Strange results but I'll keep digging.
Kurt On Sun, Jun 23, 2019, at 7:35 PM, Kurt McCullum wrote: > Thanks Steve. I'll track that down and see if I can make it work. I > appreciate the information! > > > Kurt > > On Sun, Jun 23, 2019, at 7:33 PM, Stephen Adolph wrote: >> Ah I misunderstood! sorry Kurt. >> Looks to me (page 102 of 136 in the 8201 service manual), without investing >> a ton of time on it, that U53 is the register that tracks the bank settings, >> and U38 pin 8 appears to have the signal BANK#2. >> >> Steve >> >> On Sun, Jun 23, 2019 at 10:23 PM Kurt McCullum <[email protected]> wrote: >>> __ >>> I have 3 NEC machines. 2 of them have REX units in them with the multi bank >>> setup. The third unit doesn't and I wanted to simulate part of the same >>> behavior without a REX unit. Thus the question about the bank 2 enable pin >>> somewhere on the motherboard. >>> >>> Kurt >>> >>> On Sun, Jun 23, 2019, at 5:53 PM, Stephen Adolph wrote: >>>> why do you want 2 REX? REX supports multi-bank. You can configure option >>>> rom for bank 1 and bank 2 already on one REX. >>>> >>>> On Sun, Jun 23, 2019 at 8:11 PM Kurt McCullum <[email protected]> wrote: >>>>> __ >>>>> Got a question for those who know the hardware of an NEC. I've got two >>>>> REX units in my main 8201a units. That allows me to have one rom for bank >>>>> 1 and another for bank 2. My third unit won't get much use so I wanted to >>>>> take another route to achieve the same thing. My plan is to replace the >>>>> 27C256 ROM with a 27C512 with the two ROM images on it. SARDOS in the >>>>> lower (Bank 1) 32k and UR-II in the higher (Bank 2) 32k. I know I can >>>>> hook up pin 1, which is Address 15, to a toggle switch and it will work >>>>> just fine but that requires an external switch to be added. Rather than >>>>> that, I wanted to tie pin1 of the 27C512 to the Bank 2 enable pin. >>>>> >>>>> So the question for you hardware guys, is there an easy place on the >>>>> system board to grab this signal? >>>>> >>>>> Kurt >>> >
