27 Oct
2022
27 Oct
'22
4:25 a.m.
On Thu, 27 Oct 2022, Steve Lewis wrote:
Ok, can you remind me next week perhaps?
Hehe, this
sounds like a great idea!
Did I send you my Kermit implementation or my Infocom V2 interpreter?
Nope - would love to check them out, any PALM examples. Your annotated disassemble of the Executive ROS is helping a lot, of
examples of how to do
certain things in native PALM examples. Some idea for implementing a RNG
in PALM is probably going to be needed (for any gaming).
I have implemented practically everything that is needed for the
interpreter, including the kind of virtual memory/swapping mechanism. And
of course, the ASCII-EBCDIC translation and screen output for the 64
chars/line.
Does your Kermit use the rear external IO? I
don't have any of the asynch
IO or comm. cards. But I've imagined it would be possible to attach a
WiModem232 to the rear external IO and (using 3 wires) to implement a
terminal in PALM. But being completely "CPU" based, unsure what baud rate
it could achieve. This is similar to the original Tandy Color Computer -
if you use its built in "Serial IO" connector, you can only get 1200 baud.
But if you use the "RS232 Pak" with the proper buffer, it can do 9600
baud. So, you can get a CoCo1 on the internet (or even a PET) - and I
think it actually would be possible to get a 5100 on the internet in a
similar way!
No, I have the Async/Serial I/O feature card. Originally, it only supports
up to 1200(?) baud and only half duplex, but since I have drawn the
schematics (it's only standard TTL) I know how to program it.
It has two modes, a bit transfer mode, and a byte transfer mode. The first
one is needed to find the start bit, then you can switch to byte mode and
have an interrupt after one transferred character.
The trick that I use for full duplex terminal emulation is to only use the
bit mode. I get an interrupt twice as many as the baud rate and examine
the input line to detect the start bit etc. In the same time, I output a
pending bit to be sent. With this, I ended with a speed of up to 4800
baud, already four times of the IBM supported byte mode rate.
For file transfers, I use the standard byte mode. The Kermit protocol is
made for half duplex transmission line, so there is no special protocol
handling needed. There, I can go up to 38400 baud.
Note, the I/O card is absolutely dumb. It is mainly a card with clock
dividers, shift registers and drivers/receivers. Is has no buffer,
nothing.
I have always wanted to build a bus interface card. It is a simple
open-collector I/O bus with an easy to implement bus protocol. I've dreamt
of building a bridge to an 8 bit ISA backplane in order to use simple
graphics cards and controllers like serial, parallel or even disk
interfaces. I have tons of these laying around here...
Christian