Search found 602 matches

by tcat
Tue Mar 31, 2020 9:45 am
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1053

Re: QL Add-on ROM

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 ...
by tcat
Mon Mar 30, 2020 7:43 pm
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1053

Re: QL Add-on ROM

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
by tcat
Sun Mar 29, 2020 5:06 pm
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1053

Re: QL Add-on ROM

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...
by tcat
Sun Mar 29, 2020 9:26 am
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1053

Re: QL Add-on ROM

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. ...
by tcat
Sat Mar 28, 2020 10:18 am
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1053

Re: QL Add-on ROM

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...
by tcat
Fri Mar 27, 2020 3:23 pm
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1053

Re: QL Add-on ROM

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 ...
by tcat
Thu Mar 26, 2020 8:16 am
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1053

Re: QL Add-on ROM

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...
by tcat
Wed Mar 25, 2020 8:17 am
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1053

Re: QL Add-on ROM

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...
by tcat
Mon Mar 23, 2020 5:04 pm
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1053

Re: QL Add-on ROM

Hi,

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

Tomas
by tcat
Mon Mar 23, 2020 4:27 pm
Forum: Hardware
Topic: QL Add-on ROM
Replies: 34
Views: 1053

Re: QL Add-on ROM

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 ...