Search found 172 matches

by Bill B
15 Sep 2019 22:26
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 18
Views: 446

Re: Another Home-Brew - Z180

Added the ROM address jumpers as suggested by Martin. A bit of a squeeze to fit them onto the PCB without moving everything. Not sure that I will need them. My present thought is that the ROM will just contain a boot loader, and everything else will be loaded from SD card. It makes development easie...
by Bill B
15 Sep 2019 15:18
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 18
Views: 446

Re: Another Home-Brew - Z180

Good point Martin, I will see what I can fit in.
by Bill B
15 Sep 2019 09:34
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 18
Views: 446

Re: Another Home-Brew - Z180

As suggested earlier, I have revised the circuit diagram to have a separate ROM Write Enable signal. The revised VHDL for this is: library ieee; use ieee.std_logic_1164.all; entity Z180_EC_Mem_CPLD is port ( data : inout std_logic_vector(3 downto 0); addr_lo : in std_logic_vector(7 downto 0); addr_h...
by Bill B
09 Sep 2019 21:30
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 18
Views: 446

Re: Another Home-Brew - Z180

Just looking back at the MTX circuit diagram in the manual. It uses the six inverters in a 74S04 chip as the clock source. Three of the inverters are used as output drivers, one for the CPU, one for the CTC and one for everything else, The CPU and CTC drivers each have 330R pull-ups to 5V, presumabl...
by Bill B
07 Sep 2019 22:06
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 18
Views: 446

Re: Another Home-Brew - Z180

Attached is the proposed circuit diagram for a cut down board, just CPU and memory. The UART built into the Z180 means that this board will be testable as-is. This design includes an edge connector with the minimum signals required for I/O expansion, assuming just 8-bit I/O addresses. Using an EPM71...
by Bill B
31 Aug 2019 23:06
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 18
Views: 446

Re: Another Home-Brew - Z180

Martin, That is more or less what I am proposing in terms of splitting into multiple boards. I will probably use my usual technique of ribbon cable and IDC connectors for a backplane. However the individual (daughter) boards will be hand etched PCBs and will need holes drilled for each of the IC soc...
by Bill B
31 Aug 2019 21:47
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 18
Views: 446

Re: Another Home-Brew - Z180

I have a draft PCB layout, see attached. Only slight problem, it is 9 inch x 5 inch. Too big to be convenient, and I am not sure whether my UV light box is big enough to develop a board of that size. Two options: Use a different construction method. The obvious alternative method is to use "perf boa...
by Bill B
20 Aug 2019 08:10
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 18
Views: 446

Re: Another Home-Brew - Z180

What I have is Z8S18033VSC.

The way I read the datasheet I have:
  • Z8S180 is for 5v parts
  • Z8L180 is for 3.3v parts.
It also suggests that Z8L parts are only available up to 20MHz (the higher speed needs a higher voltage).
by Bill B
18 Aug 2019 21:56
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 18
Views: 446

Re: Another Home-Brew - Z180

Attached is a planned circuit diagram. The Z180 has a 1MB external address space which is mapped onto the 64KB address space of the Z80 core in three areas, which the Zilog documentation designates as (from low internal address to high): Common Area 0 Bank Area Common Area 1 The boundaries between t...
by Bill B
13 Aug 2019 16:06
Forum: OFF TOPIC
Topic: Another Home-Brew - Z180
Replies: 18
Views: 446

Another Home-Brew - Z180

Having taken advantage of Lez Anderson's extremely generous offer of free chips for a second time, I thought I should nail my colours to the mast and publicly commit to doing something with them. What attracted me to the latest offer from Lez was the inclusion of Z180 CPUs. The idea of building a fa...