Search found 2189 matches

by 1024MAK
Thu Jan 10, 2019 8:22 pm
Forum: Hardware
Topic: Help in resurrecting my ZX81
Replies: 64
Views: 6430

Re: Help in resurrecting my ZX81

Good to hear that you have got your ZX81 working.

That board does look it has been through the wars though...

Mark
by 1024MAK
Wed Jan 09, 2019 11:38 pm
Forum: Hardware
Topic: Best solution for expanding ram to 128k on a zx48k?
Replies: 17
Views: 766

Re: Best solution for expanding ram to 128k on a zx48k?

Video RAM is the RAM used by the ULA (or gate array) to produce the video picture. In a ZX Spectrum 16k or 48k, this is always the same area of RAM in the “lower” RAM chips, that is, the 4116 chips (eight 16k chips each one bit wide). The 128k machine (and later machines) have 128k chips. The logic ...
by 1024MAK
Wed Jan 09, 2019 4:28 pm
Forum: Hardware
Topic: Best solution for expanding ram to 128k on a zx48k?
Replies: 17
Views: 766

Re: Best solution for expanding ram to 128k on a zx48k?

Paul wrote:
Wed Jan 09, 2019 12:02 pm
My programmer is a tl866
I use latest lattice settings without problems.
I am not sure whether I have a deviceID check disabled or if it's on defaults.
Kind regards Paul
Thanks Paul :D

Mark
by 1024MAK
Wed Jan 09, 2019 4:27 pm
Forum: Hardware
Topic: Best solution for expanding ram to 128k on a zx48k?
Replies: 17
Views: 766

Re: Best solution for expanding ram to 128k on a zx48k?

Before I explain further, a bit of history and a time line. Sinclair’s engineering staff developed the ZX Spectrum 16k and 48k machine’s based on what they had learned in creating the ZX80 and ZX81. The ZX Spectrum+ is just a 48k board (or a 16k board) in a new case with a slightly better keyboard. ...
by 1024MAK
Wed Jan 09, 2019 11:17 am
Forum: Hardware
Topic: Best solution for expanding ram to 128k on a zx48k?
Replies: 17
Views: 766

Re: Best solution for expanding ram to 128k on a zx48k?

Hi Mark, While this was true for several years microchip technologies is now producing chips starting with ATF. ATF16V8 for example in DIP, PLCC, SOP... Hi Paul Ahh, yes. A lot of hobby projects are/were based on the Lattice versions of the GAL chips. That is the line that has been discontinued. Be...
by 1024MAK
Wed Jan 09, 2019 10:45 am
Forum: Hardware
Topic: Best solution for expanding ram to 128k on a zx48k?
Replies: 17
Views: 766

Re: Best solution for expanding ram to 128k on a zx48k?

I'm really not sure (or technically competent enough) to evalute how I want the ram to be configured (ZX Spectrum 128k (Toastrack)/+2 (grey) or ZX Spectrum +2A / +2B (both in a black case) or a +3 / +3B). Could you please enlighten me on this? I just thought "if there's 128k ram, then there is :D T...
by 1024MAK
Wed Jan 09, 2019 10:41 am
Forum: Hardware
Topic: Best solution for expanding ram to 128k on a zx48k?
Replies: 17
Views: 766

Re: Best solution for expanding ram to 128k on a zx48k?

Careful. Only CPUs, microprocessors and microcontrollers execute assembly code. In programmable logic devices, be they PAL, GAL, CPLD or FPGA devices, what you are actually see is device configuration information. This tells the programmer how to configure the logic gates in the device so that it wi...
by 1024MAK
Tue Jan 08, 2019 3:31 pm
Forum: Hardware
Topic: Best solution for expanding ram to 128k on a zx48k?
Replies: 17
Views: 766

Re: Best solution for expanding ram to 128k on a zx48k?

I presume you mean the original rubber key model? Actually fitting larger capacity DRAM chips is not too much of a problem. The problem is adding the circuitry to provide the bank switching capability, especially if you want it to be configured to be the same as in a ZX Spectrum 128k (Toastrack)/+2 ...
by 1024MAK
Tue Jan 08, 2019 11:35 am
Forum: Hardware
Topic: Some questions about ZXPand+ serial port
Replies: 12
Views: 729

Re: Some questions about ZXPand+ serial port

Correction, it looks like the ZXpand uses the PIC to bit bash a general purpose I/O pin (also known as a software serial port). See this post where MIDI is being talked about...

Mark
by 1024MAK
Tue Jan 08, 2019 10:33 am
Forum: Hardware
Topic: Some questions about ZXPand+ serial port
Replies: 12
Views: 729

Re: Some questions about ZXPand+ serial port

Hardware handshake does not have to use processor interrupt lines. It can be done using regular (as in frequent) polling if a suitable UART chip is used. The UART chip then deals with all the RTS/CTS signalling automatically. Systems that do not use a UART chip, however, do require far more processo...