IBM 5150 Technical Reference

Error Recovery
Error recovery is handled through software. A eRe is used to
detect errors. The polynomial used
is G(X) = X16+X12+X5+ 1,
which is the polynomial used by the synchronous data link control
interface. Essentially, as bits are written to
or read from the
cassette tape, they are passed through the
eRe register in
software. After a block of data
is written, the complemented
value of the calculated
eRe register is written on the tape. On
reading the cassette data, the eRe bytes are read and compared
to the generated
eRe value. If the read eRe does not equal the
generated
eRe, the processor's carry flag is set and the status of
AH is set to hex 01, which indicates a eRe error has occurred.
The routine
is exited on a eRe error.
5-28 System BIOS

IBM 5150 Specifications

General

Brand	IBM
Model	5150
Category	Desktop
Language	English