vLA News-updated

vLA81/82/128 now all available on SellMyRetro….

After the vLA1 was completed I set myself a challenge to replicate the functionality of some of the other Sinclair ULAs, firstly the ZX81 followed by the ZX Spectrum and finishing with the Toastrack ULA (as this would leverage most of the ZX Spectrum ULA design).

I knew that all of these had been already done before but as the inner workings had not been published in detail this meant that there would be plenty of design still required (the part I enjoy the most). Armed with Grant Searle’s fantastic ZX80/81 repository and Chris Smith’s wonderful expose of the Spectrum ULA, I started about a year ago on the vLA81.

A functioning vLA81 was completed in October 2018 and work started on the vLA82, by far the most complex of the three. A working vLA82 prototype was completed in March 2019 and work was begun on the vLA128. In parallel with the design, schematics were refined, PCBs finalised, and samples sent out for testing when they became available.

A working vLA128 was completed in May 2019. Over the time the other vLAs were progressing the vLA81 underwent its own evolution. As the Xilinx XC9572XL CPLD used in the vLA81 had unused resources I decided to add some extra functionality (see features below).

The complete vLA family (so far):

Feature summary:

vLA81
1. Fits within the same 40 pin DIL socket outline as the original ULA.
2. Narrow IC pins for easy plugin ULA replacement. In most cases the existing socket will be OK.
3. Provides the same functionality as the 2C210E Sinclair ULA.
4. Video level selectable between standard video (suitable for direct connection to a 75 ohm monitor input) and high sync level (suitable for the modulator input or some video mod boards).
5. Back porch on/off select.
6. Internal 32K memory support (High or Low for the different hires schemes).
7. Programmable user configuration gives access to:

• Inverse or normal video and choice of black or white border.
• 50/60 Hz video standard.
• Ability to map ram to the ROM space (write protect enable/disable – 32K internal ram required).

8. Configuration port socket provided on PCB base for external config switch option.
9. Tested with an extensive suite of ZX81 software (full list to follow).
10. Ideal for preserving the original ZX81 ULA.
11. Low power consumption.

vLA82
1. Plugin ULA replacement. In most cases the existing socket will be OK.
2. A low profile and 40 pin DIL footprint means that the vLA82 is designed to fit in a ‘rubber key’ ZX Spectrum case without further modifications.
3. Provides the same functionality as the 6C001-7 Sinclair ULA.
4. Passes standard ULA benchmark tests (floatspy, Brendan’s Diagnostic ROM etc.).
5. Tested with an extensive suite of ZX Spectrum software (full list to follow).
7. Ideal for installing in an aftermarket Spectrum PCB without needing an original ULA.
6. Low power consumption.

vLA128
1. Fits within the same 48 pin socket outline as the original ULA.
2. Narrow IC pins for easy plugin ULA replacement.In most cases the existing socket will be OK.
3. Provides the same functionality as the Sinclair 7K010E-5/ Amstrad 40056.
4. Passes standard ULA benchmark tests (floatspy, Brendan’s Diagnostic ROM etc.).
5. Tested with an extensive suite of Spectrum 128/+2 (Grey) software (full list to follow).
7. Ideal for preserving the original Toastrack/+2 ULA.
6. Low power consumption.

If any of these items would be of interest then please email to vdrivezx@gmail.com