Atari STFM TOS upgrade

[qq1975b]

I tried with 27C010A EPROMS but I have also 27C1000 if needed (and 27C256 28 pin). Also AM27C010 but are the same as the 27C010A.

I did the schematic posted using 2x 32 pin sockets to avoid soldering the EPROMs pins. On the Mega ST is a lot of free space  .

So, there are 3 sockets: one 28 Pin attached to the motherboard, one 32pin with the lower pinout rerouting, and one 32 pin with the upper pinout rerouting.

I splitted the TOS.img in HI and LO files with ROMSPLIT app under Hatari .

The Mega 4 has TOS1.4 German in two chips. I tested it with TOS1.4 UK in two chips and worked ok too.

[Anemos]

I want to tell my schematic  already working well on STFM of my friend

[qq1975b]

Yes, that's thes scheme I followed. The one from Exxos.

How do I upload pictures here? I will burn the EPROMs again doing the img split on a real Atari...

[Anemos]

use imageshack ,and post the links

[qq1975b]

Here we go!



http://imageshack.us/photo/my-images/404/lafoto2jv.jpg
http://imageshack.us/photo/my-images/24/lafoto1sz.jpg

As I said, two sockets were used to avoid soldering on the EPROM directly.

[Petari]

I suggest that you look here for Mega ST ROM upgrade with 32 pin EPROMs :   http://atari.8bitchip.info/flashest.php

It is important that do some things with W2-W4 pads.
Text between 2 pics of Mega ST ROM upgrade:

"On pic above is how it is solved in Mega ST. 32-pin sockets are inserted in original ROM sockets, so that pins 1, 2, 31, 32 are in air. Pins 30 are cut down, and is best to put little insulator between them and sockets, to avoid contact.

Connectiing of Flash EPROMs:   pin 32:   +5V (Vcc) , add cer. capacitor between it and GND, with shortest possible legs.
                                                 pin 31:  (/WE)  /RW signal from CPU - via resistor and protection switch (explained later)
                                                 pin 30:  (A17 of Flash)    to selection switch
                                                 pin  2:   (A16 of Flash)    to A17 of CPU - it is closest at W2, point 3 .
                                                 pin  1:   (A18 of Flash)    to selection switch

Other connections in Mega ST:  W3 (remains) on pos for 1M ROMs (2-3 connected). W2: remove shortcut and connect point 3 to pins 2 of Flash EPROMs. To point 2 of W2 connect inverted RW signal of CPU (this leads to OE pins of ROMs) .
W4: remove shortcut (if there was 6 chip TOS), Lower point (ROM2 signal) goes to selection logic, upper point comes from selection logic - then need to cut (desolder) pin 12 of 74LS11 , to avoid conflict.
"

Of course, if not using Flash EPROMs and don;t want in circuit programming, you just connect +5V to point 2 of W2 - what leads to OE pins. And another not to do is:  do not cut (desolder) pin 12 of 74LS11 - it is needed if no additional logic.
Pin 31 of EPROMs go to +5V, of course.