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here i will track some things regarding rs232 emulation, and perhaps fix things while at it. It may also serve as documentation on how all those RS232 things work. Gpz (talk) 19:29, 25 July 2019 (CEST)

  • for all first tests i will use some version of CCGMS, and regular user-port rs232 emulation at 2400 baud.
  • for ACIA tests i will use novaterm or striketerm.
  • if not explicitly testing two instances of VICE, i will use cgterm as the "calling" end


I need more / better testcases. Right now i am using CCGMS, but that will hardly do for more than a few basic checks. what i am looking for is:

  • some (terminal?) program that shows the various modem control lines (dtr/dtd rts/cts CD etc) on screen in realtime
  • a minimal c*base setup that lets me reproduce c*base related bugs
    • detailed description of the supposed problems with c*base
  • other problematic programs/scenarios
  • all of the above pre-configured for a) a standard userport modem at 2400 baud and b) a swithlink at something like 38400 baud

To make this page more complete, more examples of real-world usecases would be nice.


To reproduce what is explained below, a few C64 programs and some host utilities are needed.


  • CCGMS (if you are familiar with another terminal program, that will do just as good)


  • socat (Windows binaries)
  • tcpser (use the FozzTexx fork until the changes are merged back into jim brains repo)

using a real RS232 port

This works by using the device name of your OS, VICE uses physical RS232 ports.


RsUserEnable = 1
RsUserBaud = 2400
RsUserDev = 1
RsDevice1 = /dev/ttyUSB0
RsDevice1Baud = 2400

status: working out of the box


RsUserEnable = 1
RsUserBaud = 2400
RsUserDev = 1
RsDevice1 = com6
RsDevice1Baud = 2400
  • the windows driver understands various options passed in the so called "mode string" after a colon after the ports name
  • finding out what COM port the usb adapter ended up might be tricky, you can use a tool like "Keyspan Serial Assistant"

status: working after some massaging of the code

rs232 over ip

This works by using the IP and port you are connecting to, VICE will use a TCP socket.

TODO: check if DNS lookup works ([ Domain name support in RS-232 settings})

connect two VICE instances on the same host

$ socat tcp-listen:25232 tcp-listen:25231

config instance #1

RsUserEnable = 1
RsUserBaud = 2400
RsUserDev = 2
RsDevice2 =
RsDevice2Baud = 2400

config instance #2

RsUserEnable = 1
RsUserBaud = 2400
RsUserDev = 2
RsDevice2 =
RsDevice2Baud = 2400


status: works


status: works

connect two VICE instances on different hosts

status: untested

piping to an external program

This is the unix way to talk to external programs.

Piping will be used when the first character of the device "file" name is a "|" (pipe) character.

Note: when the external program is netcat (or "nc") without further options, the result is equivalent to using "rs232 over ip" as described above.


"calling" a telnet BBS

$ tcpser -v 25232 -p 6400 -s 2400 -l 4
RsUserEnable = 1
RsUserBaud = 2400
RsUserDev = 4
RsDevice4 = |nc 25232
RsDevice4Baud = 2400



status: works


status: not implemented

TODO: a windows replacement for arch/shared/coproc.c:fork_coproc() must be implemented (this is non trivial unfortunately) and then hooked up in rs232-win32-dev.c in the same way it is on unix. once done define grep for COPROC_SUPPORT and adjust the respective places (preferably removing it)

some pointers:


  • the code is somewhat prepared
  • we should probably create another thread which monitors the launched external process, closes the pipes when the child dies, and perhaps other things


  • whether the "UP9600" (daniel dallmann) hack is being used seems to depend on the baudrate(?). this should be a seperate option

driver issues

  • handling of DTR and RTS seems to be completely missing. rs232dev_set_status, rs232dev_get_status, rs232dev_set_bps apparently are not called by the layer above

user interface

  • a couple of typical rs232 settings should probably be configurable for at least "real rs232 port at host". (behavior of DTR, RTS...)

WinVICE 1.19

a supposedly "fixed" version of WinVICE 1.19 has been floating around, which apparently contains two changes:

  • ACIA fix (whatever it is about)
  • support for the ip232 protocol

this is here

ip232 protocol

This is the protocol used by some modified WinVICE 1.19 to talk to tcpser.

TODO: (optionally!) support this protocol

NOTE: this is partially implemented now (not DTR/DCD handling)

tcpser->vice ip232.c:ip232_write

0xff nn ->
 nn = 0      DCD = false     
 nn = 1      DCD = true
 nn = 255    literal 0xff
other   ->   unchanged

vice->tcpser ip232.c:ip232_read

0xff nn ->
 nn = 0      DTR = false      note: the original patch never sends 0
 nn = 1      DTR = true
 nn = 255    literal 0xff
other   ->   unchanged


driver stack

rsuser.c                   -> rs232drv.c              -> rs232.c              -> shared/rs232dev.c
rsuser_read_ctrl (WIP)        rs232drv_set_status (ok)   rs232_set_status (ok)   rs232dev_set_status (TODO)
rsuser_write_ctrl (WIP)       rs232drv_get_status (ok)   rs232_get_status (ok)   rs232dev_get_status (TODO)
aciacore.c                                                                       rs232net.c
acia_get_status (ok)                                                             rs232net_set_status (WIP)
acia_set_handshake_lines (ok)                                                    rs232net_get_status (WIP)