Sega-Naomi

i want to start by saying a big thanks to AndyGeezer for sorting me out with the stuff to find this. :smt004





firstly the backup capacitor that always leaks.

you can and should get rid of it.

it's not needed.

it keeps power to the clock and ram so you can change the lithium battery - that's all.

the stupid thing is that acording to the datasheet, the battery should outlast the capacitor!!!

(they are rated for 1000 charges/discharges, 365 days in a year = just under 3 years - the battery probably lasts a lot longer)





now for the good bit.

THE MYSTERY BLUE JUMPERS.



JP1 is the clock select for the audio-cpu/rtc.

position1 gets the clock from the cartridge-port (cn2).

position3 gets it from the onboard clock circuits.



i suspect it's only used in position1 for multiboard stacks like airline-pilot/f355 to sync the audio chips.





JP13 is the ground connection for the Maple-Bus.

not worth explaining the detail - leave it on 3.



JP9-12 configure the serial port for 5v differential protocol or 3.3v standard serial.



pinout:

---------------------------------------

rs422 pinout:

[ jp9-12 = 2+3 ]

1-RXD

2-TXD

3-GND

4-RTS

5-CTS

6-GND

3.3v signal level(probably)

-----------

[ jp9-12 = 1+2 ]

1-RXD-

2-RXD+

3-GND

4-TXD+

5-TXD-

6-GND

5v signal level

---------------------------------------





on Naomi2 there are more:



JP5 and JP8 set options on the system controller.

(atleast i think it is)

JP5 is normally set to 3,

JP8 is normally set to 1.



JP4 is somehow tied into the cpu,

i suspect it's changing the addressing or interrupts.

it's normally set to 3.







i hope this was usefull.



btw, all N1 work was done using the newer board with part number:

(837-14230/14258-02)



if anybody has a dead/faulty N1 board of the old caged/hod2 type they dont want, then let me know.

thanks for the great info.

Can you give more info on cap? Wiant to remove from naomi 2

so remove the cap then - just snap it off if you want - you dont even need to open the casing.

Now you tell me after I replaced 4 of them! Clearing the solder from the ground hole is a total PIA!

highwayman wrote:I want to start by saying a big thanks to AndyGeezer for sorting me out with the stuff to find this. :smt004



JP9-12 configure the serial port for 5v differential protocol or 3.3v standard serial.



pinout:

---------------------------------------

rs422 pinout:

[ jp9-12 = 2+3 ]

1-RXD

2-TXD

3-GND

4-RTS

5-CTS

6-GND

3.3v signal level(probably)

-----------

[ jp9-12 = 1+2 ]

1-RXD-

2-RXD+

3-GND

4-TXD+

5-TXD-

6-GND

5v signal level

---------------------------------------

Maybe there is a typo here, "rs422 pinout" should be written on top of the second set of signals ?

on Naomi2 there are more:



JP4 is somehow tied into the cpu,

I suspect it's changing the addressing or interrupts.

it's normally set to 3.

Is it connected to one of the pins of the SH4 microprocessor ?



Another interesting thing to check is if the NMI pin of the SH4 in a Naomi 1 board is connected somewhere ...