Search found 1376 matches

by Pr0f
Tue Nov 14, 2017 10:13 am
Forum: The Welcome Area
Topic: Hello from London
Replies: 5
Views: 6488

Re: Hello from London

Welcome aboard... :-)
by Pr0f
Tue Nov 14, 2017 8:48 am
Forum: Hardware
Topic: Random hardware ideas!
Replies: 77
Views: 36207

Re: Random hardware ideas!

Was thinking about a ROM emulator that could plug into DIP28 socket or into a cartridge for the ROM port, with a RAM on board, and the ability to populate the RAM with an Image from an SD / Micro SD card. A small OLED display could act as the menu, allowing selection of the ROM image required, and s...
by Pr0f
Tue Nov 14, 2017 8:37 am
Forum: Hardware
Topic: Engineering mules....
Replies: 16
Views: 8715

Re: Engineering mules....

Although it does interrupt IPC comms and screw up keyboard access for a period of time, it should be possible for the interrupt handler to resynch it by discarding all the current work, which would mean any open serial ports, any current keyboard requests, any sound being produced... I think the onl...
by Pr0f
Mon Nov 13, 2017 11:05 am
Forum: Hardware
Topic: Engineering mules....
Replies: 16
Views: 8715

Re: Engineering mules....

Was the code to allow redirection of the CTRL-ALT-7 interrupt not present in earlier ROM's then? From the 8049 disassembly it seems to stop all interrupts in the 8049 IPC, and then go into a double loop of counting down before restarting the IPC, but it does set that Interrupt IPL2 line, which with ...
by Pr0f
Mon Nov 13, 2017 7:21 am
Forum: Hardware
Topic: Engineering mules....
Replies: 16
Views: 8715

Engineering mules....

Does anyone know of any early hardware prototypes of the QL ?

Any add on boards - for instance, what ever the CTL ALT 7 intercept device was, was it only software, or was there hardware for that too?

Just curious to know what is out there... :)
by Pr0f
Sun Nov 12, 2017 1:51 pm
Forum: Hardware
Topic: Microdrive Unit Design
Replies: 118
Views: 58948

Re: Microdrive Unit Design

For reading (taken from js rom disassembly): ;Initialise microdrive registers L52B8 move.w #256,d0 ;initial attempts move.w #$0F0F,d3 ;initialise checksum moveq #0,d4 moveq #pc..rxrd,d6 ;port bit for read buffer ready lea pc_trak1-pc_mctrl(a3),a2 ;microdrive read track1 port lea pc_trak2-pc_mctrl(a3...
by Pr0f
Sun Nov 12, 2017 11:08 am
Forum: Hardware
Topic: Microdrive Unit Design
Replies: 118
Views: 58948

Re: Microdrive Unit Design

I think the calculations are fine, but work for 4 bits not 8, so the bandwidth is double for 8 bits, or to put another way, your time for 8 bits should be doubled - in a logical sense the 2 heads make the tape double the length, although I suspect the heads are interleaved to guarantee the throughpu...
by Pr0f
Sun Nov 12, 2017 10:19 am
Forum: Hardware
Topic: Microdrive Unit Design
Replies: 118
Views: 58948

Re: Microdrive Unit Design

Technical docs and hardware shows there are 2 heads, so your calculations need to reflect that 2 heads are in use.
by Pr0f
Fri Nov 10, 2017 11:45 am
Forum: Hardware
Topic: PSU alternative?
Replies: 71
Views: 58417

Re: PSU alternative?

This is just half wave rectification, Sinclair being cheap again ;-) The current requirements for the +12 and -12v are so light, they can get away with this, and the ripple is easily dealt with by the regulator..
by Pr0f
Thu Nov 09, 2017 10:01 pm
Forum: Software & Programming
Topic: QubATA 3.10 I/O area address
Replies: 9
Views: 5524

Re: QubATA 3.10 I/O area address

In theory is it possible to have the hardware registers at a different address, i.e. not in the last 256 bytes, assuming the GALS are set to a different address?