Schematics for 7c81

Thanks for clarifying that, can the 7c81 use all three ports and use the 2 x RS422/485 ? I think i was reading somewhere if you enable the RS422/485 then the third port is disable or cannot be used ?

There is no connection between the Parallel ports and the RS-422/485 interfaces,
however if you have a large configuration like 5ABOBx3 with 13 Stepgens, there is not
enough room for the 2 SSerial ports (though there may be room from UARTs)

The parallel ports are always usable as GPIO though, so on a 5ABOBx2 configuration
the third port can be GPIO

I think i will design the Port one as a Parallel out and port 2 as a Parallel in and use 74HCT245 as output IC's and 74LVC245 as the input IC's. As per these schematics :

 

The 74 245 are quite plentiful:
www.lcsc.com/search?q=74HCT245
www.lcsc.com/search?q=74LVC245

And then output with terminal screw that resemble my breakout board i posted.

Port 3 will i leave as through hole for later development or prototyping.

I see there are a lot of SP491 available from this supplier so i will just copy the RS-485 Schematics www.lcsc.com/search?q=SP491

how is the progress on this schematic ?

It is going good, manage to fuse the 7c81_5abobx2d.bit to spartan 6 and playing around with Xilinx ISE 14.7 for custom builds. I have ordered some IC SP491 and 74lv04 that i am waiting for to test modbus, also waiting for 7I92TH from mesa.

After testing and playing around i will complete circuit with EASYEDA, in the end i will probably have FGPA with 2 x Parrellel ports(16 output/18inputs) and 2 x Serial/modbus ports replacing the  PI5C16211 with SN74HCT245N



This is a really steep learning curve for me because i am new to FGPA's but i will try and get this done

How much that will cost from easyeda ?

I will have to finish pcb and see how much if i order on jlcpcb, but i think it will be a lot more expensive than buying from mesa because they have a min order of 5 pcb.

UPDATES

I manage to compile bit file and write it to Spartan 6 xl9.  I did try to use a generic bit file (7c81_5abobx2d.bit) but my clock pin is different than on the mesa 7c81 board  (P50 -> P55) so had to first figure out how to do that. I used Xilinx ISE 14.7 and this link Making bitfiles for MESA Hostmot2 boards added missing source file and got it compiled.

 
 
 
 

I can now play around with the electronics

 

 

Thanks for the link
Is that your FPGA board or a dev board (any more info on it)?

I bought it on Aliexpress  

 

I have also added the schematics and PCB layout. NOTE on the schematics it says 25Mhz Oscillator it is actually 50Mhz.

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