Tarbell Electronics -- Cassette Interface
This was the board that launched the company and made
Tarbell a household word in the world of the S-100 bus.
The board could read and write data at up to 540 bytes /second. The "standard"
Tarbell format however was 187 bytes/second. Nevertheless this was far
better than the only other current non machine specific format at the time the
"Byte/Lancaster" format which was only 30 bytes/second. The encoding
method was a phase-encoded (exclusive-OR of clock and data), self-clocking
system. The board would work with almost any decent commercial audio
cassette. Though it was nicer to be able to control the tape in software with
proper digital cassette recorders and reel to reel recorders. The board
was flexible to any port address via an onboard dip switch. There were on
the board extra status and control lines that could be utilized to control the
cassette recorder (or indeed anything else).
The board came well equipped with software to read and write tapes though
numerous versions and improvements circulated in user groups and later in CP/M
archives.
One problem that helped keep his board from completely dominating the field
was that in an early shipment of boards, the plated-through holes weren't
properly done. In order to get the boards to work, a high percentage of the
leads had to be soldered twice--once on each side of the board. If that was
done the boards worked fine, and the extra time needed was not great, but
during the period while the problem was being diagnosed the board's
reputation got badly tarnished.
The manual for this board can be obtained
here.
Other Tarbell Electronics
S-100 Boards
Cassette Interface
Single Density FDC
Double Density FDC
32K RAM
Z80 CPU Board
This page was last modified
on
05/14/2016