U11 pin 10 and pin 15. I think bank 2 occurs when Pin 15 is 0 and pin 10 is one.
U53 pin 10 should indicate when bank 2 ram is in use as an upper ram block. Bank 2 ram can replace the Roms also in the lower 32k. On Monday, June 24, 2019, Kurt McCullum <[email protected]> wrote: > 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 > > > > > >
