Hello,
I try to build the Serial Board from Wendell Sander.
https://apple1notes.com/wp-content/uploads/2020/07/Apple-1-Serial-Board-Documentation.pdf
Wendell wrote in his documentation that a VMA mod is needed on the Apple 1 board with an A 2200 ohm resistor in parallel with a 100 pf capacitor.
He write also according to the VMA jumper setting ...
"This makes the Serial board useable even if there is no VMA mod made"
So my question is, if it will be possible to use Wendells serial board with the replica 1 plus?
Do have somebody experience with this board and replica 1?
Thanks Thorsten
Hello,
my PCBs Serial Board V3 are delivered and a started build up the board.
My first try was a fail!
I tried to inialize the 6551 ACIA dicribed in the documentation.
D004: 8b 96
I 'm not shure, but I think if you write memory
D004.D005 have to give back
8B 96
That does not work. I can't write to this memory location (D004?)
It is not possible to get a serial connection with a terminal.
I think there must be an Problem with the 6551 circuit!
Further Test setup.
VAM-Jumper open
I try the switches:
I)
keyboard switch on
Monitor switch off
No keybard function on Apple 1, nor serial Terminal
II)
keyboard switch off
Monitor switch on
No keybard function on Apple 1, nor serial Terminal
No character shown if typing on Apple 1, nor serial Terminal
III)
keyboard switch off
Monitor switch off
again keybard function on Apple 1, nor serial Terminal
again character shown if typing on Apple 1, all works fine
some remarks:
I have to change some components to modern ones, bacause some parts are not available and out of stock and discontinued.
But I use original 6551 from Rockwell and the serial components
National Semiconductor DS14C89AN Line ReceiverNational Semiconductor DS14C88N Line Driver
So it should be like the original BOM parts. für serial funktions.
I test 5V points and ground connectivity on all ICs. Voltage seams ok. 4,9V up to 5,1V
Do you have any idea how to bugfix this? What could be the next steps or test scenarios to narrow down the cause?
Thanks Thorsten
D004:8B 96(no space between : and 8)
Hello,
I tried with and without blank. In my experience it doesn't matter.
I take some pictures write into $0004 and $D004.
Adress $0004 no problem $d004 not writable.
Write 0004.jpg
Try write D004.jpg
The Briel Replica I has no address-decode jumpers, correct? So it will need to be programmed to decode the appropriate address ranges for the I/O card, or modify the card to fit into the address-decoding map the Replica already is using.
I try the card on my apple 1, too.
Same effect. I can' t write anything to D004 to D005
I have two pictures from the memory map.
On replica map the address range for Pia is declared from $D000 up to Dfff,
on Apple 1 map from $D010 up to $D012
Maybe the replica can't run the card bacause of overlapping adress range?
Wendell write in documentation...
"The Apple 1 Serial board uses a 6551 ACIA. The addressing for this board has been designedto mimic the Apple 1 6820 PIA at the $D01X locations and still provide full access to the 6551in the $D00X space. ...This means that the serial board operates exactly like the 6820and there are no software changes of any kind to use the serial board. On the other hand thefull set of Serial Board 6551 registers are still available at locations $D002 to $D005...."
So if I understand, is the adress region $D002 up to $D005 the register of the 6551 Acia on the Board.
$D010 upt to $D012 is replaced threw the Board, if toggle swiches are on and the serial interface do the work.
That coult be io on my board, bacause if i swich on Keyboard the apple 1 keyboard is not in funktion.
If I switch off keyboard works.
I think, there must be still an Hardwareproblem I have to solve with the 6551 ACIA circuit...
Memory Map Replica.jpg
Memory Map Apple 1.jpg