Hi, All the SRAM backed protection, makes me thinking about mechanical bank switching on 512K eeprom, as I can address only 256K upper or lower halves. Here I rely that a reverse leakage is big enough to pull address line high, and not that big to be pulled low with a switch. I know resistors could ...

Hi Dave,

I see your point, battery backed SRAM, similar to what Martin has proposed. This flip-flop is a write-protection trigger, right? As I believe just to write enable, SDWL signal should suffice or not?

Many thanks for taking your interest.
Tomas

Hi, Thinking further. On AM29F040 /OE seems complementing /WE as per the specs. While CPU R/W (RDWL) could wire directly to /WE, /OE needs to be inverted. This may require extra RW GAL input, correct, could this work? VALID_ROM = A19 * A18 # $C0000 ROM_CE = VALID_ROM * DS IF( VALID_ROM ) DSMCL = 1 I...

Hi All, Many thanks for useful arguments. I wish to explore in theory, what I could do with `29F040', fitted in a daughter board above `Simple RAM' based on `AS6C4008', if proved possible to program right on QL bus. It should serve primarily as read only media, holding extensions mentioned earlier. ...

Hi, Yes, EDIT preprogramming the flash outside the QL machine, seems easiest. To act as a ROM inside QL, /WE is then fix wired to be kept high. I have seen various circuits on the net, that use a diode (IN4148), probably to pull signal high or low, or initiate some delay on power on. Still do not ge...

Hi, Thank you. I will probably go with $C0000 address decode, as I do not have wired A17 line, so it may be easier, also this way I could use up to half of the EEPROM capacity 256K. In the glue logic, I drive both RAM /OE and /CS with GAL's /RAMCE pin. CPU R/W is connected directly to RAM /WE. I am ...

Hi, Thanks for all the input, digesting (1 of 100% complete). I am also thinking of `venturing' something simple of my own, me capable of. Looking back at `Simple RAM' these are GAL equations, I pulled together with the help in the forum here. GAL16V8 Glue logic for 512x8 SRAM Sinclair QL RAM Expans...

Hi, Some statistics on versions I use on my QL. 16K TKII 16K PTR_GEN 12K HOT_REXT 12K WMAN 40K qpac2 8.0K ramprt 4.0K SERMouse 108K total Provided QPAC is or can be made romable easily. This may fit $E0000-$FFFFF which is 128K. I was hoping to use either eeprom AM29F010 (128K, 8x16K sectors) or AM29...

Hi,

I see, now to avoid internal expansion port, what other option we could have. A daughter board piggy backing over ROM chips?

Tomas

Hi, EDIT Looking at ROM extension port, it provides some [all] address, data lines, and ROMOE. romport.png It would be nice to see the extended environment on standard QL system, so I was hoping to put, TKII, PE, QPAC, RAMPRT and SerMouse on the flash EEPROM, but I am not quite sure if they are all ...