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trs80: Improve RS-232 driver

I could drive my RC2014 from my TRS-80 4P (using the Remote Shell
coming in the next commit)! A challenge I faced was that the RC2014
spits characters too fast and the CTS line of its ACIA modules
(both the 6850 and SIO/2 ones) are hard-wired to ground, making
flow control difficult. I solved this, for now, by lowering comm
speed.

This driver improvement makes CL<? faster and makes baud rate
configurable in CL$.
This commit is contained in:
Virgil Dupras 2021-01-03 13:56:53 -05:00
parent 772c0c4fe4
commit 0f83451193
3 changed files with 35 additions and 6 deletions

View File

@ -9,7 +9,7 @@ Load with "602 LOAD".
There is also the RECV program at B612.
( ----- 602 )
1 8 LOADR+
1 9 LOADR+
( ----- 603 )
CODE (key?) ( -- c? f )
A 0x08 LDri, ( @KBD )
@ -100,10 +100,19 @@ EXX, ( unprotect BC ) ;CODE
: FD! ['] @WRSEC SWAP FD@! ;
: FD$ ['] FD@ ['] BLK@* **! ['] FD! ['] BLK!* **! ;
: CL$ 0x02 0xe8 PC! ( UART RST ) 0xee 0xe9 PC! ( 9600 bauds )
0b01101100 0xea PC! ( word8 no parity RTS ) ;
( ----- 611 )
: CL$ ( baudcode -- )
0x02 0xe8 PC! ( UART RST ) DUP 4 LSHIFT OR 0xe9 PC! ( bauds )
0b01101101 0xea PC! ( word8 no parity no-RTS ) ;
: CL> BEGIN 0xea PC@ 0x40 AND UNTIL 0xeb PC! ;
: CL< BEGIN 0xea PC@ 0x80 AND UNTIL 0xeb PC@ ;
CODE _
0xea INAi, 0x80 ANDi, IFZ, PUSH0, ELSE,
0xeb INAi, PUSHA, PUSH1, THEN,
;CODE
: CL<? _ IF 1 EXIT THEN
0b01101100 0xea PC! ( RTS )
1 TICKS ( 100 us ) _
0b01101101 0xea PC! ( no-RTS ) ;
( ----- 612 )
( We process the 0x20 exception by pre-putting a mask in the
(HL) we're going to write to. If it wasn't a 0x20, we put a

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@ -28,3 +28,16 @@ can be raised) very much. We have to take extra care, when
communicating from modern system, not to send too much data too
fast. But for COS-to-COS communication, this simple system
works.
# Broken hardware
Some designs are broken with this scheme. For example, the
RS2014 SIO module hard-wires CTS to GND because the FTDI
connector doesn't have such a pin (modern computers can always
handle the load).
In these cases, a solution would be to use Break signals as a
workaround, but I prefer avoiding complexity for now. So when
you deal with broken design, you'll have to sidestep it either
by implementing your own Break handling or by lowering com-
munication speed.

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@ -270,8 +270,15 @@ means there's a limit of 100 blocks per disk.
You'll need to send those blocks through RS-232. First, let's
initialize the driver with CL$. This driver does not require
the TRS-DOS driver to be loaded. Also, it is hardcoded to
"no parity, 8 bit words, 9600 bauds". Now, let's have the CL
take over the prompt:
"no parity, 8 bit words". And takes a "baud code" as an argu-
ment. It's a 0-15 value with these meanings:
00 50 01 75 02 110 03 134.5
04 150 05 300 06 600 07 1200
08 1800 09 2000 0a 2400 0b 3800
0c 4800 0d 7200 0e 9600 0f 19200
After CL$ is called, let's have the CL take over the prompt:
' CL> ' EMIT **!
' CL< ' KEY **!