HD63C09/MC6809 RC2014 module

[Tadeusz Pycio]

Please verify the schematic. I have no experience with this architecture, so I could have made some obvious mistakes. The RC2014 module is supposed to work with a typical ROM/RAM module and a 16C550 UART. Circuits without an integrated clock oscillator are available in the second circuit and are not subject to counterfeiting.

[Nick Brok]

Hi, TSC should be connected to ground for a appropriate working of the 6809E

If left floating sometimes the address and databus are tristated. Look at my schematic of Scrumpel8d as a working example.

https://cdn.hackaday.io/files/1818237779115232/scrumpel8dr3.pdf

Op donderdag 1 december 2022 om 13:10:11 UTC+1 schreef Tadeusz Pycio:

[Tadeusz Pycio]

Hi Nick,

Thank you for this comment, I have made corrections to the schematic (in addition I have connected the missing CLK signal to E).

There is a Hitachi note in the file regarding interference on the bus. It is required to include these resistors on the data bus for such a simple system?

[Alan Cox]

I didn't - it works fine on my 2MHz 6309 parts. but the RC2014
backplane is a big long beast with lots of capacitance. I did put
extra buffers on the 6303 CPU card for similar reasons as the 6303 is
sensitive to high capacitive loads when the address lines switch.

Alan

[Tadeusz Pycio]

Hi Alan,

Further improvements incorporating your suggestions. I will not be able to set I/O addressing to FE00-FEFF without changing to GAL20V8, I could only make an adjustment to FC00-FDFF. If it's relevant, it might be worth using a larger GAL, which will give more flexibility on occasion (e.g. a jumper to change the I/O space from FE00 to FF00). What are your thoughts on this?
What about the CLK signal on the RC2014 bus? Leave the E there or use XCLK?

[Alan Cox]

On Thu, 1 Dec 2022 at 16:43, Tadeusz Pycio <ta...@wp.pl> wrote:
>
> Hi Alan,
> Further improvements incorporating your suggestions. I will not be able to set I/O addressing to FE00-FEFF without changing to GAL20V8, I could only make an adjustment to FC00-FDFF. If it's relevant, it might be worth using a larger GAL, which will give more flexibility on occasion (e.g. a jumper to change the I/O space from FE00 to FF00). What are your thoughts on this?

You don't want I/O at FFxx because you've got the vectors at the top.
FCxx ought to push the I/O to the top of memory so should work.

Flex assumes E000-FFFF is occupied by the system monitor and other
such stuff. Flex itself wants
RAM C000-DFFF and 0000- wherever.

Cubix by default has RAM 2000-DFFF and ROM E000-FFFF, however the area
you stuff the BIOS in starts at F9CC so in practice there is plenty of
room as the BIOS for a CF adapter is tiny (my CF and 16x50 BIOS ends
at about FB30 and would probably work with your card if you just
replaced FExx with FCxx). I think you'd get a floppy driver in the
FExx space. If not you could steal some of the low 8K which Cubix
doesn't use in the default build as it's meant for MMIO, screen memory
etc.

> What about the CLK signal on the RC2014 bus? Leave the E there or use XCLK?

For the 6803/6808/6809 cards I used the input clock because the input
clock is 4 x E which conveniently means that a 2MHz part runs nicely
with the standard RC2014 CLK frequency.

For 6502 CLK is E, but with a modern 65C02 or 65C816 you can just
about run at the RC2014 clock although I had to tweak the 512/512K
card to use one AHCT part to make it work. Does fly though 8)

Alan

[Tadeusz Pycio]

I have designed the PCB, the only change is the XCLK is on the CLK of the RC2014 bus. Now I have to wait to test this module in the real world. This is a completely unknown architecture for me, Motorola 6800 products were not popular in my country. Thank you for your help.

[Alan Cox]

On Thu, 1 Dec 2022 at 23:34, Tadeusz Pycio <ta...@wp.pl> wrote:

I have designed the PCB, the only change is the XCLK is on the CLK of the RC2014 bus. Now I have to wait to test this module in the real world. This is a completely unknown architecture for me, Motorola 6800 products were not popular in my country. Thank you for your help.

Except for the Tandy machines and some French systems I don't think the 680x/68HC11 made much impact in the home computer space, but in the embedded world they were (and still are) all over the place. In keyboard controllers, in older (pre ARM) appliances, in burglar alarms etc.

 

Nice.. no vias ?

Alan

[Tadeusz Pycio]

Nice.. no vias ?

 

Hi Alan,

No, there are three, besides that would be plagiarism. ;-)

[Tadeusz Pycio]

The PCB is ready, now I have to get this one in working order, it will be fun ;-)