The Norwegian Connection
From ARE LEISTAD in Oslo, two programs to speed data transfer
via the BBC Micro
THE BBC Micro is ideally suited for the transfer of data over
the telephone. In Norway we regularly transfer programs, data
files and memory blocks via the RS 423 port with a 300 baud modem,
which is just as readily available in the UK.
All you need is the software given here.
Program I automatically places the transferred data in the same
memory locations in the receiving BBC Micro as in the transmitting
one. This is the program that we use most of all.
Program II enables the receiver to place the received file wherever
he wishes in memory by specifying the start address.
This can be quite useful when transferring programs from cassette-based
to disc-based computers and vice versa. It is also a little bit
more memory efficient.
Both listings are well labelled with REMs to explain how they
work.
The modems must, of course, be connected and working properly
before any communication can start. One can use a relatively cheap
and simple modem, either acoustic or direct-coupled. There is
no need for modems offering duplex, auto-dial or other facilities.
This is the procedure we use:
1. Put both BBC Micros in Mode 7 (to save memory).
2. LOAD or *LOAD the transmitting micro with the desired program
or file. Don't forget to note the start address and length.
3. Set PAGE to a high value in both micros - say &7000 -
and CHAIN program I or II.
4. Select RX or TX as required and enter the appropriate addresses
or lengths.
5. Set the modem to the correct mode, such as call/answer or
transmit/receive. Start receiving and transmitting, and wait for
the process to be completed, which is indicated by a beep. 6.
When completed, the transferred data can be SAVEd or *SAVEd onto
disc or tape. When using normal SAVE with Basic programs remember
to reset PAGE and type OLD. Machine code programs, data files
and such must be *SAVEd in the normal manner, using the correct
addresses.
This method works very well with Basic and machine code programs,
data files or whatever is present in the BBC Micro's memory.
The programs are only tested on 300 baud but they will probably
run at much higher speeds due to the immense speed possible with
the BBC Micro.
