Tandy 1000 HX Technical Reference Manual page 422

The structure and usage of the clock service routine is as
follows:
32
HEX Offset From Length and
Segment 0040:0000 Intended Use
6CH
6EH
70H
1 word - Least significant 16 bits
of clock count
1 word - Most significant 16 bits
of clock count
1 byte - Twenty four hour rollover
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