ReCo6502 Guide
Installation |
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Installation of ReCo6502 in your Acorn 6502 Second Processor proceeds as follows.
1) Disconnect your Second Processor from both the mains and your BBC, and open it up.
2) Identify the power wires (one is brown (+5V), one is black (ground)), and unplug them from the PCB.
3) Remove the PCB (along with the permanently attached flatcable).
4) Replace it with the ReCo6502 PCB, and plug in the supplied 40-wire Tube cable. Take care of matching the 'pin 1' side of the cable (marked by the only coloured wire) with the 'pin 1' sides of the cable sockets on the BBC (marked on the bottom of the machine, near the socket) and ReCo6502 (marked by a 'V' shaped symbol on the socket).
5) Transplant the Tube ULA, from the socket nearest the Tube cable connector on the original PCB, to the socket nearest the Tube cable socket on ReCo6502 (the ULA should be marked 'Ferranti' and 'ULA9C018E-7', or very similarly). Use e.g. a flat headed screwdriver to gently lever the ULA out of its socket, alternating sides. Take care of matching the 'notches' on the ULA and its new socket. See also *) below.
6) Plug in the power wires (the brown wire connects to the tab marked '+5V', nearest the PCB edge, the black wire connects to the other tab near it), and check and double-check that you did it correctly.
You should now have something resembling this picture :
7) Check that the link settings on ReCo6502 are correct (refer to the following sections).
8) Close up your Second Processor, and reconnect it to both the mains and your BBC.
*) Note that you may also use the Tube ULA from a 65C102 Co-processor for the BBC Master (the ULA should be marked 'AMI' and '2201,266', or very similarly). But then you MUST also single-power ReCo6502 (normally, it is dual-powered) or you will destroy the ULA. Refer to 'Power' for details on how to single-power your ReCo6502.
Establish orientation on the ReCo6502 PCB. Looking at the side where the components are, with the Tube cable socket to your left, take note of 'north', 'south', 'east' and 'west' (e.g. the power tabs are now 'south-west').
There are four notable sockets. Starting 'west', going 'east', they are : the 40-pin Tube cable socket, the 40-pin Tube ULA socket, the 40-pin processor socket, and (passing the 32-pin RAM chip) the 28-pin ROM socket.
There are also four sets of links (that allow configuration of ReCo6502) :
They will be referred to, respectively, as the 'processor', 'configuration', 'ROM' and 'power' links. They will be discussed in the following sections. An individual link from a set will be referred to by a number that increases from 'west' to 'east'. E.g., of the processor links, the 'west' or leftmost one is number 1, the 'middle' one is number 2, and the 'east' or rightmost one is number 3.
ReCo6502 supports the following processors :
The processor links (refer to 'Sockets and links' for their location) need to be set differently in each case :
| Processor | Link 1 | Link 2 | Link 3 |
|---|---|---|---|
| Original 65C02 | closed | open | closed |
| WDC 65C02 | open | open | closed |
| WDC 65C816 | open | closed | open |
'Closed' means : place a jumper on the link pins. 'Open' means : don't place a jumper on the link pins (but store it in a safe place for possible later use).
Note that you must select a suitable processor clock frequency with the configuration links (refer to 'Configuration' for details). Select 3.15 MHz for the original 65C02, and 14.7 MHz otherwise.
ReCo6502 supports two sizes of ROM :
The ROM link (refer to 'Sockets and links' for its location) allows selection of the active boot code :
| ROM size | Boot code | Link |
|---|---|---|
| 32 KB | no choice | west |
| 64 KB | set 1 active | east |
| 64 KB | set 2 active | west |
'East' means : place a jumper on the eastmost two link pins. 'West' means : place a jumper on the westmost two link pins.
In a 64 KB ROM, boot code set 1 is located at offsets 0x0000 through 0x7FFF, and set 2 at offsets 0x8000 through 0xFFFF.
A standard ReCo6502 comes with a 32 KB ROM, containing a new Tube OS (which is the original Tube OS 1.10 with optimisations, bugfixes, and ReCo6502 specific extensions) and a copy of Hi-BASIC (refer to 'Configuration' for details about its use). The image of the standard ReCo6502 ROM is supplied in the 'ReCo6502ROM' file. Refer to the Use section for more information about 'ReCo6502ROM_816' and 'ReCo6502ROM_02'.
In addition, the 'Tube6502ROM' file contains the image of a ROM that is suitable for the original 6502 Second Processor, and the 65C102 Co-processor for the BBC Master. Simply program it into a 2732 PROM, and use that to replace the original on-board ROM. Of course, this does not magically offer any ReCo6502 specific features, but it does provide optimisations, bugfixes, and the *GoS command.
The configuration links (refer to 'Sockets and links' for their location) allow selection of the default configuration (or 'hard config') of ReCo6502, and enable or disable the 'soft config' (which allows more precise configuration of ReCo6502).
Link 1 selects the processor's clock frequency :
| Frequency | Link |
|---|---|
| 3.15 MHz | north |
| 14.7 MHz | south |
'North' means : place a jumper on the northmost two link pins. 'South' means : place a jumper on the southmost two link pins.
Link 2 enables or disables the auto-load of the on-board HiBASIC. Set it 'south' to enable, or 'north' to disable.
Link 3 enables or disables the 'soft config'. Set it 'south' to enable, or 'north' to disable. Refer to 'Soft config' for details.
Note that the processor's clock frequency can be selected on-the-fly by software as well. Refer to 'Programming interface' for details.
Normally, the Second Processor is 'dual-powered'. This means that it is powered by both the host and parasite power supplies (the former powers the host side of the Tube ULA, the latter everything else). Host power arrives via the Tube cable. Parasite power arrives via the black and brown wires plugged into the Second Processor's PCB.
The Second Processor can also be 'single-powered', which means that it is powered entirely by either the host or parasite power supply. Single-powering is MANDATORY if you use the Tube ULA from a 65C102 Co-processor for the BBC Master. If such a Tube ULA is dual-powered it will be destroyed.
The power link (refer to 'Sockets and links' for its location) must be 'made' to single-power ReCo6502. It connects the host and parasite power supplies. Therefore one of them must be left unconnected (or the power supplies will be short circuited and possibly destroyed).
Disconnecting the parasite power supply is easiest. Simply unplug the black and brown power wires from the ReCo6502 PCB. Your Second Processor will now be entirely host powered, and therefore you no longer need to switch 'on' your Second Processor (but you can no longer switch it 'off' either).
Disconnecting the host power supply is harder. It requires a special Tube cable that has had its five +5V wires disconnected. Contact me if you want details. If you use such a cable, your Second Processor will be entirely parasite powered.