Todd,
PEEK and POKE will READ/WRITE to Memory. You need to look for a command to
INPUT and OUTPUT a byte to I/O space.
In QBasic, you could write:
a = INP(&h20)
and
OUT &h20, b
I don't know MBasic, but would love the feed back when or if you find these
commands.
If these commands are not available, look for a way to execute a machine
language program and then I can help you with the 8080 codes to load the
accumulator and output. I think it's 3E to load, D3 to output and CD to return
but let me confirm. Inputing will be more tricky.
Now... here's what you need to OUTPUT and INPUT to talk to the 8250 UART.
BASE I/O Address for 1st Uart (used as console) is 0x20
The 2nd UART is at 0x28
My code below which is part of the firmware configures the UART for 9600 BAUD.
Please read the data sheet for 8250 for other baud rates.
(The clock is 18.432Mhz divided by 10).
MVI A,80H ;Set baud rate
OUT UART0+3
OUT UART1+3
MVI A,12 ;12=9600 baud
OUT UART0
OUT UART1
MVI A,0
OUT UART0+1
OUT UART1+1
MVI A,3 ;Set 8 data bits, no parity, 1 stop
OUT UART0+3
OUT UART1+3
Where it says UART1+3, that makes it I/O address 0x2B
You can skip the baud setting if you don't wish to deviate from 9600, N,8,1
Next, to Send a byte... you must first test to see if the Transmit buffer is
empty (or still sending the previous byte), then send the byte.
Here's the 8080 code that does that.
LOOP IN UART0+5
ANI 20H ;TEST FOR TX HOLD REG EMPTY
JZ LOOP
POP PSW
OUT UART0
So, INPUT IO at 0x2D and test for bit 0x20 to be SET or ON, if not ON, then
stay in loop.
When it's OFF, then output to 0x28 the desired byte.
eg, quick basic
100 a=INP(&H2D)
110 if (a and &h20) = 0 then 100
120 OUT &h28, char
Receiving data uses the flag at bit 1, like this.
200 a=INP(&H2D)
210 if (a and &h01) = 0 then 200
220 char=INP(&h28)
Hope that helps. Good luck!
Regards,
Josh
Date: Sat, 11 Apr 2015 17:04:31 -0700
From: [email protected]
To: [email protected]
Subject: [N8VEM-S100:6719] CP/M or Basic and COM Ports....
I have Josh's 8080 board with COM1 being the console and
a ver 2.0 Console I/O board mirroring input/output on VGA.
Josh's board has a second COM port and I would like
to send text strings to it in Basic....
I have an old Digital DECtalk voice synthesizer I want
to play with. I have a Mbasic manual but didn't see
anything, perhaps I could 'PEEK" it, but I don't know
how to talk to the UART.
Anyone have an idea on or point me in a direction ?
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