Common TTL and CMOS Logic Gates

November 26, 2018

I been using a lot of TTL and CMOS logic gates in my recent RC2014 circuits and after realising that I had loaned out my much used copies of TI’s TTL Logic data books some time again and never got them back so to help me I created this quick comparison table for the common TTL and CMOS logic gates.

For completeness here’s a logic truth table:


eDay7

October 31, 2018

We were at eDay again earlier in the month (Saturday 6th October 2018) as part of Newcastle Maker Space. This is the seventh year its been going and as usually we had a great time showing off various projects.

We had the following R-Kade and PiZythn and Rc2014 projects on show.

For those who don’t know what eDay is: eDay is a local digital skills day where various digital technologies are demonstrated to an enquiring general public. A sort-of geeky show and tell where local groups and individuals meet at Gateshead Central Library and show off their projects or what interests them.


8052 CPU card for RC2014 Bus

August 31, 2018

A few months ago I mentioned a 8031/8052 CPU card I had designed for the RC2014 bus. Here’s a couple of pictures for an assembled card. I’m just starting to test it out so I will post results shortly.


New RC2014 boards: RS232 and 8052

April 24, 2018

I got a bumper box of PCB’s in the post today, just in time for Maker Faire UK 2018 this weekend (29th/30t April 2018).

Inside the box were some new RC2014 boards. The first two new PCB’s were my respins of a Z80 SIO/2 serial board and a Raspberry Pi Zero terminal board, as well as two brand new designs.

The first brand new board was a RC2014 RS232 breakout board allowing TxD1/RxD1 and/or TxD2/RxD2 serial signals from the RC2014 bus to be driven at RS232 levels.

The second brand new PCB was a new 8052 CPU board. This is a bit of an experimenters board as the 8052 bus architecture doesn’t directly map onto the Z80 bus architecture. When using the 8052 CPU some of the Z80 control bus signals (!M1, !MREQ, !IORQ etc.) will need pulling low via jumpers when attempting to make use of other cards. So why all the fuss. Well, the 8052 CPU does have the excellent the 8052-BASIC available which does make it a fun and a powerful (in 1980/1990 micro terms 🙂 ) system.


RC2014 Prototype Board

February 23, 2018

The Prototype card is one of the very first cards I designed for the RC2014 system.

It’s larger than a normal RC2014 card but that is intentional so you have as much prototyping area as possible for building a circuit.

It features both the classic single row pin-header for the original RC2014 pin-out and also a double row pin-header for the newer enhanced RC2014 bus pin-out.

 

 

You can find them on my Tindie store


RC2014 Z80 System with enhanced bus

January 28, 2018

I’ve been busy with my big box of PCBs and I here’s my first Z80 system design and build. It comprises of the following:

– Z80 CPU card
– 8K ROM & 8K SRAM card
– 68B50 ACIA card
– 5-slot enhanced+ backplane

It’s pretty much a standard Z80 layout but I’ve expanded the bus to the latest Enhanced Bus definition for all the cards. The 5-slot backplane uses double row (2×39) female pin headers to include the RC2014 enhanced bus and in addition I’ve added an extra set of address lines (A16 to A23) for the possibility of using 16-bit CPU’s (8086/68000) and memory options (upto 1MB) in the future.

Here’s some pics of the various cards:


Z80 Card

Memory Card

 

ACIA UART Card

 


Big Box of PCB’s

December 27, 2017

Christmas came slightly early this year when a big box of PCB’s arrived.

Inside the box where a bunch of PCB’s for making guitar effects boards.

As well as a bunch of PCB’s for my take on a RC2014 Z80 based retro computing system.

More pics to follow when I’ve built them up.