Parallel Data Transfer V2
If you can get the User Port to behave
as if it were a printer then you have
a simpler way of transporting data from
any computer with a printer port to the
beeb, i.e no baud rate etc. to worry
about. This adaptor does just this, the
program then saves the incoming data to
a previously opened file when the tran-
sfer is complete pressing ESCAPE closes
the file.
The printer side of this adaptor can
either have a centronics socket into
which the normal printer lead may be
plugged or you could connect direct to
the source computer.
Adapter diagram
---------------
N/C
O X O O O O O O O
N/C
O X O O O O O O O
BUSY
O X O O O O O O O
ACK
O X O O O O O O O
bit 7 bit 7
O X O O O O X O
bit 6 bit 6
O X O O O O X O 0v
bit 5 bit 5
O X O O O O X O 0v
bit 4 bit 4
O X O O O O X O 0v
bit 3 bit 3
O X O O O O X O 0v
bit 2 bit 2
O X O O O O X O 0v
bit 1 bit 1
O X O O O O X O 0v
bit 0 bit 0
O X O O O O X O 0v
STROBE CB2
O X O O X O O X O 5v
CB1
O O O O O O O X O 5v
Centronics User Port
Side Side
Track direction is across the screen.
N/C not connected
X indicates cut track.
Both grounds need to be connected
together to provide a common reference
Function
--------
When the BUSY signal is low
8 bit data comes in the centronics
side, then the strobe pulse is sent
which causes a CB1 interrupt, raising
the BUSY signal. After dealing with
the data, BUSY is again set low.
Signals
-------
STROBE.is sent by the computer when the
data is valid.
ACK..is an output of the printer which
tells the computer it has received
the last character sent and is
active low.
BUSY.is an output of the printer which
when high tells the computer not
to send any more data.
DATA IN
STROBE IN
ACK/BUSY OUT
The program
-----------
There are two modes of operation :-
Binary mode
All data is passed and saved.
Check for characters ignored, not sent
to the printer by the transmitting
computer.
Ascii mode
Character 10's (line feed)
are not saved, this tidies documents
from various machines as there is no
standard set order of the line feed
and carriage return that may mark the
end of each line.
Also there is a routine to ignore
standard printer commands and some
Epson commands, these can be tailored
to individual needs.
In this mode text is written to the
screen (80 columns) so you can see what
is being saved, this has the bonus of
method of seeing a document before
being printed saving valuable paper.