Sc126 and KERMIT... seems to be difficult

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ITSecurity Guy

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Mar 8, 2026, 7:29:12 AM (12 days ago) Mar 8
to RC2014-Z80
Hi, using "minicom" (on a Linux system) and the SC126 via FTDI Serial Connection is not really a secret, and XModem works (although I had to use RTS/CTS flow control with 115200 Baud).
With the same connection, I was not able to use the Kermit protocol, not with "minicom" and KERCPM3 (generic Kermit for CP/M 3.0) and not with Tera Term (and of course a Windows PC).
I already tried to reduce the baud rate, but it does not help.
Is it possible to use the Kermit protocol with a 2nd FTDI Serial Connector (named "Serial B") ? Or must I even use an additional SIO card (hopefully not) ?
I've read the 2nd serial connector does not support RTS/CTS flow control, is that true ?
Thanks for any hint related with the SC126 and the Kermit protocol ;-)

Richard Deane

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Mar 8, 2026, 7:55:29 AM (12 days ago) Mar 8
to rc201...@googlegroups.com
I use Kermit occasionally, and have the SC126 and SC131. 

On a default romwbw build, console is on port A with HW handshaking,  the Z180 second serial port DOES NOT have HW handshaking.
Kermit will not work across the active console connection (but xmodem can). I think kercpm3 will default to lst so use device command to define LST to port B. I do not think that Kermit requires hardware handshaking.

There is a simple change & rom rebuild  (well it was when I did it a year or so ago, but I can't remember the tweak in the bios source) what will swap ROMWBW to use second port for A and the first port for B if you really need handshaking on B to get kermit working.

I used real kermit on windows  (https://www.kermitproject.org/k95.html).

Hope this helps
Cheers
Richard

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Steve Clarke

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Mar 8, 2026, 10:08:19 AM (12 days ago) Mar 8
to RC2014-Z80
I use kermit regularly on my SC130 running CP/M 3. I have ckermit on my linux desktop. Using the second serial port is entirely possible with some speed limitations due to the lack of rts/cts. I find 9600 is 100% rock solid, but have had success up to 19,200 with the z180's cpu speed increased.  

On the SC130: 
mode com1 9600 
device AUX:=com1
kerm3vt
set flow off
connect

On the PC:
ckermit
set line /dev/ttyUSB0
set modem none
set speed 9600
set carrier-watch off
send <file>

It's not quick but it does work.

Steve Clarke

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Mar 8, 2026, 6:37:47 PM (12 days ago) Mar 8
to RC2014-Z80
Actually, I made a mistake. I can run up to 38400 baud with the standard 18Mhz cpu clock.
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