...
Choosing the output
Using the above truth table was difficult. Connecting the other inputs to the desired state i.esignal that we wish to control as the Enable signal, choosing which out put is used is determined by A0 and A1. In this case they are both high, which means that Y3 is used.
- ROE to E (Pin 15)
- Vcc to A0 (Pin 14) for A19 high
- Vcc to A1 (Pin 13) for logic 1
...
This procedure was repeated for
- ROE to E (Pin 15)
- Vcc to A0 (Pin 14) for A19 high
- GND to A1 (Pin 13) for logic 0
...
| CE | A19 | LOGIC 1 | ROES |
|---|
| 256K FLASH PROTECTED | X | 1 | 1 | 1 |
|---|
| 256K FLASH | 1 | 1 | 0 | ROE |
|---|
| 512K RAM | 0 | 0 |
|
|
|---|
Connection List 512K
| E | A0A1 |
| PIN
No |
|
|
|
|
|
|
| I/O |
| PIN
No |
|
|
|
|
|
|---|
| FROM Z88 SE1 | I | E | 1 | 1 | 0 |
|---|
110x | MA190 | x0x11 | LOGIC 1 - Vcc | 0x1 | 10 | 00 | Y0 | 4 | 1 | 1 | 1 | 1 | 0 |
|
| O | Y0 | 12 | 1 | 1 | 1 | 1 | 0 |
|---|
| TO FLASH CE | O |
|---|
0 | 0 | 10Y2 | 6| 1 |
| TO FLASH ROE_S | O | Y2 | 10 | 1 | 1 | 0 | 1 | 1 |
|---|
| O |
|---|
0 | 1 | 1 | TO FLASH ROE_S | O | Y3 | 9 | 1XX1...
Connection List 1M
| I/O |
| PIN
No |
|
|
|
|
|
|
| I/O |
| PIN
No |
|
|
|
|
|
|---|
| FROM Z88 SE1 | I | E | 1 | 1 | 0 |
|---|
11 A190 | x A190x | 0x1 | 1 | FROM Z88 SE1 | 0x1 | 1| 0 |
| TO RAM CE | O | Y0 | 4 | 1 | 1 | 1 | 1 | 0 |
| TO FLASH ROE_S | O | Y0 | 12 | 1 | 1 | 1 | 1 | 0 |
|---|
| TO FLASH CE | O | Y1 | 5 | 1 | 1 | 1 | 0 | 1 |
|---|
TO FLASH ROE_S |
|
| O | Y1 | 11 | 1 | 1 | 1 | 0 | 1 |
|---|
| O | Y2 | 6 | 1 | 1 | 0 | 1 | 1 |
|
| O | Y2 | 10 | 1 | 1 | 0 | 1 | 1 |
|---|
| O | Y3 | 7 | 1 | 0 | 1 | 1 | 1 |
|
| O | Y3 | 9 | 1 | 0 | 1 | 1 | 1 |
|---|
Conclusion
It has been a long journey to get to this point, but we are pleased to report that a hardware solution has been found.
...
https://tinyurl.com/mkdlwv4
512K Flash Modifications
Image Removed
Image Added
| Pin | Pin | Pin | Instruction |
| Pin |
|
|---|
|
|
|
| Cut track (ROE) underside from pin 24 | U3 | 24 | 512K FLASH |
| U4 | 13 | 14 | 15 | Lift up pins DO NOT CONNECT TO PCB |
|
|
|
| U4 | 13 |
|
| (SE1) CE A19 - Connect to | U4 | 12 |
|
| U4 |
| 14 |
| A19 (SE1) CE - Connect to | U4 | 21 |
|
| U4 |
|
| 15 | ROE - Connect to VIA | U1 | 37 |
|
|
|
| 1M FLASH | U4 |
| 1110 |
| ROE_S Connect to | U3U1 | 2437 | 512K FLASH OE |
1M Flash Modifications
| Pin | Pin | Pin | Instruction |
| Pin |
|
|---|
|
|
|
| Cut track (ROE) on top going to | U1 | 37 | 1M FLASH |
| U4 |
| 4 | 5 | Lift up pins DO NOT CONNECT TO PCB |
|
|
|
| U4 | 13 |
| 14 | 15 | Lift up pins DO NOT CONNECT TO PCB |
|
|
|
| U4 | 13 |
|
| REMAINS ON GND |
|
|
|
| U4 |
| 14 |
| (SE1) CE - Connect to | U4 | 1 |
|
| U4 | 14 | Connect to Vcc |
|
| U4 | 15 | ROE - Connect to | U3 | 24 | 512K FLASH |
| U4 |
| 1112 |
| ROE_S Connect to | U1 | 37 | 1M FLASH |
...