Terminal Module - RCA COSMAC Operator's Manual

TERMINAL MODULE
The Terminal Card, in conjunction with serial/parallel
conversion routines in the Utility Program, provides an
ASCII interface to a bit. serial terminal, such as a
Teletype. The card has connectors appropriate for two
different electrical communication interfaces, either
standard 20 rnA current loop or TTL levels.
The serial ASCII characters which are output to the
terminal are formed by strobing Data Bus bit 0 into a latch
under program control. Data is transmitted to memory by
driving External Flag 4. The Utility Program samples
EF4 at appropriate intervals and builds an ASCII character,
one bit at a time.
I/O STROBE
DATA BIT 0
c
TTL DATA
20MA DATA
TO TTY
EXTERNAL,..-_""",
FLAG 4
TERMINAL SELECT
c
" " " - - - - - - - TTL DATA
Fig.14: Block Diagram - Terminal Module
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