Search found 443 matches

by Nasta
Thu Jan 27, 2022 1:43 pm
Forum: Hardware
Topic: Dead SuperHermes - any hints/tips for investigation?
Replies: 26
Views: 4232

Re: Dead SuperHermes - any hints/tips for investigation?

If the EPROM code is available, it might be possible to 'refresh' the part but it will require skipping over the 'check blank' part as the part will not be blank. Usually some zero bits will revert to ones which is the un-programmed state. I think there was a flash version of the same PIC chip but h...
by Nasta
Fri Dec 24, 2021 12:01 pm
Forum: Hardware
Topic: USB Keyboard IF
Replies: 37
Views: 8062

Re: USB Keyboard IF

It is an 8x8 matrix, thus 64 keys (mind the double shift keys!). However, shift, ctrl and alt are treated with extra diodes because there are some limitations to what keys can be pressed without 'phantom' keypresses being generated. Won't go into why here, suffice to say shift-ctrl-alt can be presse...
by Nasta
Sun Nov 14, 2021 10:37 pm
Forum: Hardware
Topic: External QL microdrive?
Replies: 17
Views: 4443

Re: External QL microdrive?

An internal microdrive cannot be directly connected to the MDV connector because, unlike the external microdrive, most of the motor control components components are on the QL motherboard. Of course, it would be possible to re-create these circuits on an extra PCB which could then be connected to th...
by Nasta
Wed Oct 27, 2021 9:21 pm
Forum: Hardware
Topic: Hermes status
Replies: 87
Views: 17589

Re: Hermes status

Here is a very interesting vendor from Poland that has several available batches of 8749 IPC chips. Ignore the first 4 which are one time programmable used, hence already programmed and not erasable. https://www.ebay.de/str/tvsatelectronic/IC-Microcontroller/_i.html?_storecat=18701871014&_sop=2&...
by Nasta
Wed Sep 29, 2021 6:45 pm
Forum: Hardware
Topic: PIC for 8049
Replies: 13
Views: 3314

Re: PIC for 8049

you could combine the functions of both chips into something larger - but then it starts to become a question of how much compatibility to the original QL you want to maintain. Certain things are expected at certain addresses, such as the RTC, Interrupt registers and mask - and the serial write reg...
by Nasta
Wed Sep 29, 2021 5:32 pm
Forum: Hardware
Topic: Hermes status
Replies: 87
Views: 17589

Re: Hermes status

Damn! I could potentially have picked up thousands of these back in the 1990's. BT used 8749 as controller on their 30-channel PCM cards. Just before I left I scavenged a dozen of the cards thrown in a skip. They also used Ferranti ULAs - never found any info on them though. May be worth having a p...
by Nasta
Sun Sep 26, 2021 10:03 pm
Forum: Hardware
Topic: CAPSLED
Replies: 28
Views: 8510

Re: CAPSLED

I think this could be reduced to a single high efficiency LED and resistor...
by Nasta
Tue Sep 21, 2021 2:39 pm
Forum: Hardware
Topic: Expanding the QL's address space beyond 1M (+primer on building QL compatible machines)
Replies: 30
Views: 8117

Re: Expanding the QL's address space beyond 1M (+primer on building QL compatible machines)

Added RAM Once the idea of extra RAM included on the motherboard is on the table, two obvious questions arise, which are what kind of RAM and how much. These are actually connected because of the available packaging and price the RAM comes in. In general, we are dealing with two types of RAM chips: ...
by Nasta
Mon Sep 20, 2021 12:40 am
Forum: Hardware
Topic: New Sockets For Old
Replies: 4
Views: 1447

Re: New Sockets For Old

mk79 wrote:Pretty all my QLs are Samsung builds and they used two cheap 24-pins sockets to host the CPU.
Exactly what should have been done from the start!
by Nasta
Sun Sep 19, 2021 6:09 pm
Forum: Hardware
Topic: Hermes status
Replies: 87
Views: 17589

Re: Hermes status

Pr0f wrote:so is it ok to post dissassembly (partial) on here now then?
I would think yes since Lau was ready to give out the source, when he manages to find it...