> Message-ID: Johan Heuseveldt wrote: > I'm sort of 'designing' a CoProcessor with a 6809 - 2 MHz version (68B09). > I refound the schematics for the internal CoPro 80186, but couldn't find > anything else. With my own 6502 external 2ndProcessor, I've investigated a http://mdfs.net/Tube and follow the link to Circuit Diagrams which will take you to http://mdfs.net/Info/Comp/BBC/Circuits You will also find the circuit diagram for the Acorn 6809 System CPU card. Note that the Tube connector pin numbers are the pin numbers of the ribbon cable header on the CoPro PCB, *NOT* the pin numbers of the plug at the host computer end. You have to rotate it to get the "correct" numbers, ie 1->40, 2->39, etc. At http://mdfs.net/Tube/6809 you will find information on other home-made 6809 CoPros. Particularly interesting is Graham Toal's at http://mdfs.net/Tube/6809/Toal which actually uses the Tube ULA and implements the Tube API. It is incredibly simple: 6809 CPU, 64K SRAM, Tube ULA and PAL to decode addresses. I'd recommend a similar design, but also add a ROM. Graham used a battery-backed SRAM, programmed it in a computer, unplugged it, and plugged it into the CoPro! I'd recommend the following design, based on the 6502 CoPro which is a R/W memory-mapped CPU, instead of a RD/WR IO-mapped CPU: +--------+ +------+ +-----+ +------+ | D0|=====| 64K |====| 4K |============| Tube | | 6809 ..| | SRAM | | ROM | | ULA | | D7|=====| |====| |============| | | | | | | | | | | A0|=====|A0 |====|A0 |============|PA0 | | ..| | | |.. | |.. | | A15|=====|A15 |====|A11 |============|PA2 | | | | | +-----+ | | | W/R|-----|W/R |-----+---------+---\ | | | | +------+ | |NAND>--|PRD | | E|--------------+---|---------+---/ | | | | | | +--\ | | | | | +--|NOT>--+---\ | | | | | +--/ |NAND>--|PWR | | | +-------------+---/ | | | NMI|------------------------------------|PNMI | | IRQ|------------------------------------|PIRQ | | RST|------------------------------------|PRST | | | | | A15---------+-----\ | | .. | | | | A9---------+ | | | A7---------+ | | | .. |13-NAND>----+---------------------|PCS | A3---------+ | | +--\ +------+ +------+ +--\ | | ---|NOT>--|RESET |--->RAM CS A8--|NOT>--+-----/ +--/ |TOGGLE|--->ROM CS +--/ +------+ If you look at the 6502 circuit diagram, you'll see that: All access to &FEE0-&FEFF goes to the Tube ULA All writes (other than the Tube ULA) goes to RAM After RESET, all reads (other than the Tube ULA) goes to ROM After a Tube ULA access, all reads (other than Tube) goes to RAM In other words, on RESET, the memory map is filled with reflections of the ROM. The startup code copies the ROM to RAM by effectively doing FOR A=&F000 TO &FFFF:?A=?A:NEXT. Any access to the Tube ULA toggles off ROM access so all further reads come from RAM. > few things. It appears that the power connections to the TUBE chip are more > advanced than I first assumed, which makes sense as this chip - besides the The Tube ULA is always powers from the host (the Beeb) as a host peripheral. The parasite system has its own power supply which powers everything else, though all parasite systems have links to allow the parasite to be powered from the host instead. On the external 6502 you would unplug the power connectors and make LINK 1. I've had a Z80 CoPro inside a Beeb for years like this. Graham Toal also wrote some 6809 client code, but his only source is in a meta-language. I am gradually translating this into 6809 assembler, and making the APIs available via defined calls. Do you have any preferences? The 6809 has three SWI entries, so I could use SWI 0-15, SWI2 0-15 or SWI3 0-15. Or any other block of sixteen entries (eg SWI2 &F0-&FF). > doesn't have pin numbers Crumbs, you're right. Anybody have a PDF-to-editable document convertor so App004.pdf can be edited and corrected? +------------+ 1|GND1 ~PNMI|40 2|Vcc1 ~HIRQ|39 3|FVcc DRQ|38 4|Vcc2 ~PRST|37 5|GND2 ~PIRQ|36 6|HD0 PD0|35 7|HD1 PD1|34 8|HD2 PD2|33 9|HD3 PD3|32 10|HD4 PD4|31 11|HD5 PD5|30 12|HD6 PD6|29 13|HD7 PD7|28 14|HA0 PA0|27 15|HA1 PA1|26 16|HA2 PA2|25 17|R/~W ~DACK|24 18|~HCS ~PWR|23 19|theta2 ~PRD|22 20|~HRST ~PCS|21 +------------+ TUBE ULA -- J.G.Harston - jgh at arcade.demon.co.uk - mdfs.net/User/JGH BBC BASIC for 30+ platforms - http://mdfs.net/Software/BBCBasic