Kevin's Blog

I want to ROM-ify the messing about I’ve been doing with the AY-3-8910 driver and video code, so I need to figure out what boot-strapping is required to get a basic Z80 machine up and running from power-on.

I have some 62256 256 KBit SRAM (32Kx8) that I’m not sure about.

The ZX Spectrum video is now working satisfactorily as described in Part 2 but when I came to use it I found applications often expected to have the 50Hz video scan interrupt which was originally generated from the ULA based on the video synchronisation s…

Having looked at the basics in part 1 and created a simple output example in part 2, I now want to turn to some kind of input example.

I’m messing around with some code ported over from the ZX Spectrum and one of the things it is doing is a fairly common trick – it uses the HALT instruction to get the Z80 to wait for a regular external interrupt on /INT to come in.

I was lucky enough to get my hands on a ZX81 in a box recently.

This post brings together a number of ideas so far from the following: ZX Spectrum Compatible Video for RC2014 Simplified Pico VGA – Part 2 Watching a Z80 Bus from an RP2350 – Part 3 It runs the code from the Spectrum Compatible video adding the video out…

I thought it time to take a proper look at the Amstrad Target board, seeing as I’ve managed to find myself an Amstrad CPC 464.

This is a continuation of fault finding and (hopefully) fixing my ZX Spectrums.

As part of my tinkering with the RC2014 I wanted an easy way to transfer ZX Spectrum compatible assembly over to an RC2014.

Having spent far too long chewing over how the Raspberry Pi Pico Scanvideo library works over in Simplified Pico VGA, this post actually starts to do something with it.

The Raspberry Pi Pico Hardware Design Manual has an example board that shows how an RP2040 can be used to create a VGA signal using a 3-way 5-bit resistor DAC.

After the final successes of the past post, I thought it would be worth formally building a diagnostic module that can be used to help debug the system should the need arise.