Time-Outs - IBM AT 5170 Technical Reference

• The class for hex 80 to BF is reentrant. There is no
restriction on the number of tasks that may access the device.
• The class for hex CO to FF is non-interrupt. There is no
corresponding interrupt for the wait loop. Therefore, it is the
responsibility of the dispatcher to determine what satisfies
r ' \
this condition to exit the loop.
Function Code Classes
Type Code (AL)
Description
00H->7FH Serially reusable devices; operating system
must serialize access
80H->OBFH Reentrant devices; ES:BX is used to
distinguish different calls (multiple 1/0
calls are allowed simultaneously)
OCOH->OFH Wait only calls; there is no complementary
POST for these waits--these are time-out
only. Times are function-number
dependent.
Function Code Assignments
The following are specific assignments for the IBM Personal
Computer AT BIOS. Times are approximate. They are grouped
according to the classes described under "Function Code
Classes".
Type Code (AL)
Time-out Description
OOH yes (6 second) fixed disk
OlH yes (2 second)
diskette
02H
no keyboard
~,
OFDH
yes
(1
second-write) diskette motor start
9-18 Compatibility