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Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Sat Sep 11, 2021 1:07 pm
by Jmstein7
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Sat Sep 11, 2021 1:46 pm
by Jmstein7
If you want to see what I'm working on, I have the repository here:
https://github.com/jmstein7/65c02-FPGA-with-Acia
This repository contains HDL for a Xilinx Cmod A7 32T FPGA, which has onboard SRAM. The FPGA is connected to a WDC65c02 (see the XDC file). The ROM (rom_mon.coe) has a simple monitor. There is a 65c51 ACIA emulated. However, I cannot get the RX to work.
The ACIA Clock input is an external oscillator that runs at 1.8432 The Clock input is an external oscillator that runs up to 6mhz.
The ACIA used here is actually written by another member here, LIV2 (Matt Harlum). Maybe Matt can figure out why RX won't work?
Jon
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Sat Sep 11, 2021 8:20 pm
by Jmstein7
I had originally put this on the backburner since I didn't think there'd be any interest outside of me using this to make cheap SSC clones, but I had never considered the use case of people wanting to put ACIAs in 3.3V systems.
I've got some free time this weekend, and already picked up two picos a while back, so I can start messing around with this. I'm positive I saw a post a while back about someone already having done the work of building a 6502 bus interface for the Pico, so really all that will be needed here is to implement the ACIA itself as a wrapper around the Pico's built-in UART.
Well, put it back on the front-burner! It's a very useful project (if it works). There are no ACIAs for 3.3v.
Jon
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Tue Sep 21, 2021 6:26 am
by fachat
I'm wondering if anyone knows of any microcontroller (PIC18F or 16F, Arduino, ESP32, Teensy, etc.) projects out there that can emulate a 65c51 or 6551 ACIA? I'm doing projects at 3.3v, so my standard WDC 65c51s won't work (5V only).
I've searched, but I'm not turning up anything that fits the bill, e.g., one of the projects I found for teensy requires all the Address lines(?). That's not going to happen. Control signals, Data Lines, and register select, i.e. That's all I can do.
Thanks!
Jon
Frankly I wouldn't look at the ACIA. I believe it has been designed with a modem being on the other end, so rts/cts handshaking is useless eg for null modem connections. Also it has no FIFO to reduce the risk of loosing characters.
I'd either look at a UART or, if you endeavor something original, writing a kind of 'fixed' ACIA with good handshaking and FIFO.
André
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Tue Sep 21, 2021 1:26 pm
by Jmstein7
I'm wondering if anyone knows of any microcontroller (PIC18F or 16F, Arduino, ESP32, Teensy, etc.) projects out there that can emulate a 65c51 or 6551 ACIA? I'm doing projects at 3.3v, so my standard WDC 65c51s won't work (5V only).
I've searched, but I'm not turning up anything that fits the bill, e.g., one of the projects I found for teensy requires all the Address lines(?). That's not going to happen. Control signals, Data Lines, and register select, i.e. That's all I can do.
Thanks!
Jon
Frankly I wouldn't look at the ACIA. I believe it has been designed with a modem being on the other end, so rts/cts handshaking is useless eg for null modem connections. Also it has no FIFO to reduce the risk of loosing characters.
I'd either look at a UART or, if you endeavor something original, writing a kind of 'fixed' ACIA with good handshaking and FIFO.
André
But, André, what about for people who already have the ACIA written into a substantial portion of their code? Doesn't it make more sense to avoid throwing out the baby with the bathwater? At the very least, should it not be register-compatible?
Jon
PS Like so many others here, I love your work!
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Tue Sep 21, 2021 2:23 pm
by fachat
I'm wondering if anyone knows of any microcontroller (PIC18F or 16F, Arduino, ESP32, Teensy, etc.) projects out there that can emulate a 65c51 or 6551 ACIA? I'm doing projects at 3.3v, so my standard WDC 65c51s won't work (5V only).
I've searched, but I'm not turning up anything that fits the bill, e.g., one of the projects I found for teensy requires all the Address lines(?). That's not going to happen. Control signals, Data Lines, and register select, i.e. That's all I can do.
Thanks!
Jon
Frankly I wouldn't look at the ACIA. I believe it has been designed with a modem being on the other end, so rts/cts handshaking is useless eg for null modem connections. Also it has no FIFO to reduce the risk of loosing characters.
I'd either look at a UART or, if you endeavor something original, writing a kind of 'fixed' ACIA with good handshaking and FIFO.
André
But, André, what about for people who already have the ACIA written into a substantial portion of their code? Doesn't it make more sense to avoid throwing out the baby with the bathwater? At the very least, should it not be register-compatible?
Absolutely. I probably missed that this is replicating an existing design.
In that case I'd go for a 'fixed' or even improved ACIA.
PS Like so many others here, I love your work!
Many thanks! Great to hear!
André
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Tue Sep 21, 2021 2:52 pm
by Jmstein7
Many thanks! Great to hear!
André
You bet! One day, I would love to implement your OS (GeckOS) in a design!
Jonathan
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Tue Sep 21, 2021 8:28 pm
by plasmo
The basic ACIA function is not complicated. Since I use CPLD in my 6502 and Z80 designs, I generally put a basic ACIA in a 64-macrocell CPLD and still have logic resources left for a small bootstrap ROM and address decodes.
Maybe people are interested in a "65ACIA" where an ACIA fits in ATF1504 and have logic leftover for RAM/ROM/IO decode?
Bill
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Wed Sep 22, 2021 12:55 am
by Michael
Maybe people are interested in a "65ACIA" where an ACIA fits in ATF1504 and have logic leftover for RAM/ROM/IO decode?
Could you put a simple "6550 ACIA" in a 22V10, please?
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Thu Sep 23, 2021 2:50 am
by plasmo
Maybe people are interested in a "65ACIA" where an ACIA fits in ATF1504 and have logic leftover for RAM/ROM/IO decode?
Could you put a simple "6550 ACIA" in a 22V10, please?
22V10 only has 10 flip flops; a basic ACIA needs about 40 or so flip flops so hardware ACIA won't fit in a 22V10. However, it may be possible to do bit-bang serial port with a 22V10. A 22V10 plus a shift register may be enough to implement a bare-bone hardware serial receiver and software bit-bang serial transmitter.
Bill
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Thu Sep 30, 2021 7:48 am
by LIV2
The basic ACIA function is not complicated. Since I use CPLD in my 6502 and Z80 designs, I generally put a basic ACIA in a 64-macrocell CPLD and still have logic resources left for a small bootstrap ROM and address decodes.
Maybe people are interested in a "65ACIA" where an ACIA fits in ATF1504 and have logic leftover for RAM/ROM/IO decode?
Bill
Would love to see this, even stripped down my 6551 takes ~80 macrocells
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Mon Oct 04, 2021 3:18 am
by jmthompson
The basic ACIA function is not complicated. Since I use CPLD in my 6502 and Z80 designs, I generally put a basic ACIA in a 64-macrocell CPLD and still have logic resources left for a small bootstrap ROM and address decodes.
Maybe people are interested in a "65ACIA" where an ACIA fits in ATF1504 and have logic leftover for RAM/ROM/IO decode?
Bill
Would love to see this, even stripped down my 6551 takes ~80 macrocells
This is the direction I've been thinking of going as well, rather than messing around with a Pico. I am hoping to jam it into a 1504, but if that's too tight there's also the possibility of using a 72 MC XC9572XL (3.3V, but 5V tolerant). The only downside to the 9572XL is that it isn't available in PLCC-44 anymore, but the TQFP-44 isn't too hard to solder; I have two here I mounted on DIP-44 adapters for a previous project. In fact it might even be possible to jam one onto a pin-compatible DIP-28 adapter. If the RS-232 level converter chips are OK with 3.3V it should even work as a drop-in replacement on existing boards.
Re: 65c51 or 6551 ACIA microcontroller or SoC Emulators?
Posted: Mon Oct 04, 2021 11:34 am
by plasmo
I design in schematic to maximize CPLD resource utilization. Attached is the current schematic of
CRC65 CPLD which is EPM7064S, a 64-macrocell CPLD available in PLCC44 package. In this design it contains
- 64-byte boot ROM
Double-buffered serial receiver at 115200 N81
Software bit-bang transmitter operating at 115200 N81
Compact Flash interface
I2C interface, bit-bang
RAM decode
Bill