Search found 16 matches

by monsonite
18 Mar 2019, 18:03
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 40
Views: 1612

Re: Expansion bus

In response to mwwhited Once you have an expansion bus capable of SPI and banks of RAM, there are many ways in which this project could evolve. At the moment - the Gigatron cpu is intimately tied to the process of generating video, consuming much of the processors available clock cycles - but this n...
by monsonite
15 Mar 2019, 18:31
Forum: Hardware and software hacking
Topic: Extending WozMon
Replies: 3
Views: 101

Re: Extending WozMon

I have started to look at extending WozMon with a disassembler mode. This is mainly a learning exercise to familiarise me with vasm, but be a useful new feature in its own right. vasm is a fairly simple language to disassemble - because most of the instructions are only 2 bytes. (Compare this with Z...
by monsonite
13 Mar 2019, 21:48
Forum: Hardware and software hacking
Topic: Extending WozMon
Replies: 3
Views: 101

Extending WozMon

Last June, Marcel ported the classic 1976 Apple 1 monitor program "WozMon" to Gigatron - and with this new tool in place, Tiny BASIC followed on very shorty afterwards. Just this week, WozMon has allowed the debugging of the expansion pcb - without the need for any external resources - untethered to...
by monsonite
10 Mar 2019, 11:32
Forum: Escape Meta Alt Control Shift
Topic: Makespace Cambridge next Saturday
Replies: 3
Views: 88

Re: Makespace Cambridge next Saturday

Hi Marcel, A nostalgia trip to the birthplace of the British Computing industry? Many notable machines were developed in Cambridge - including EDSAC (6th May 1949) and of course the Acorn and Sinclair home computers (and many others). And from tiny Acorns - mighty ARMs were built. I'd like to attend...
by monsonite
08 Mar 2019, 20:30
Forum: Hardware and software hacking
Topic: 10MHz and Beyond!
Replies: 3
Views: 506

Re: 10MHz and Beyond!

Hi All, After a year of inactivity - I have caught the Gigatron bug again. In May 2018 I was able to tweak the clock frequency up to 10.00MHz and still have the Blinkenlights run - just 160% of their normal speed. Tonight, I have reduced the value of C1 and C2 in the crystal oscillator circuit from ...
by monsonite
24 Feb 2019, 18:28
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 40
Views: 1612

Re: Expansion bus

Marcel,

Many years ago (1981) I bought an expansion board for a ZX81. For 8-bit output it used a '273 and for 8-bit input a '244.

There was probably another device like a '139 to decode /IORQ and some of the address lines - It was as simple as that.



Ken
by monsonite
23 Feb 2019, 12:19
Forum: Hardware and software hacking
Topic: Expansion bus
Replies: 40
Views: 1612

Re: Expansion bus

Hi Marcel, Joerg, The concept is really starting to take shape - like Marcel I like a diagram to help explain things - thanks for the pdf. Regarding parallel I/O - might I suggest the MCP23S17 which is a 16 bit port expander driven from the SPI bus. http://ww1.microchip.com/downloads/en/devicedoc/20...
by monsonite
28 Jan 2019, 18:11
Forum: Hardware and software hacking
Topic: Gigatron emulator in a µC
Replies: 2
Views: 229

Re: Gigatron emulator in a µC

Hi Joerg, That is really cool! A Gigatron emulated with so little hardware! Did you work out first that you needed 36 ARM instructions to emulate the most complex Gigatron instruction - so that set your clock at 36x6.25MHz = 225MHz. 225MHz is about 34% increase in clock speed for the normally 168MHz...
by monsonite
29 Oct 2018, 08:12
Forum: Hardware and software hacking
Topic: Pluggy McPlugface PS/2 adapter is available
Replies: 10
Views: 731

Re: Pluggy McPlugface PS/2 adapter is available

I believe that those USB to PS/2 adaptors are entirely passive - and work with keyboards that were designed generate both USB and PS/2 communications protocols. The keyboard must sense if it has been plugged into USB or PS/2 and behave accordingly - and the adapter just makes sure the signal and pow...
by monsonite
16 Aug 2018, 20:41
Forum: Hardware and software hacking
Topic: FORTH
Replies: 3
Views: 422

Re: FORTH

Hi Nuxi, Forth is 50 this year - recently some original 1968 assembly listings for the IBM 1130 came to light, with Charles Moore experimenting with an early Forth. From the 50 year old listings, you see how Chuck builds up his Forth from the ground up using a few primitives, which exploit every fea...