Thanks Steve. I pulled out the tech manual and it does seem like that is the right pin. I've got a unit split open so I'll check later tonight to see if it's pulsing as Brian suggested. Could be the case. From the diagram, I was hoping it would be 5v when selected and 0v when grounded.
Kurt On Mon, Jun 24, 2019, at 12:51 PM, Stephen Adolph wrote: > I'll take another look tonight.. > > On Mon, Jun 24, 2019 at 11:36 AM Kurt McCullum <[email protected]> wrote: >> __ >> 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 >>>>> >>> >>
