Tandy 1000 HX Technical Reference Manual page 420

The equipment check BIOS call (INT 11H) and memory size
BIOS call (INT 12H) return information from the following data
areas:
The structure and usage of the floppy disk driver RAM data
area is as follows:
30
HEX Offset From
Segment 0040:000
10H
13H
Length and
Intended Use
Devices installed word
Memory installed word
HEX Offset From
Segment 0040:0000
3EH
3FH
40H
41H
42H
Length and
Intended Use
1 byte - drive recalibration status -
bit 3-0, if 0 then drive 3-0
needs recal before next seek
bit 7 indicates interrupt
occurrence
1 byte - motor status - bit 3-0 drive
3-0 motor is on/off, bit 7 -
current operation is write,
requires delay
1 byte - motor turn off time out
counter (see Timer ISR)
1 byte - disk status - codes defined
below
7 bytes - 7 bytes of status returned
by the controller during
result phase of operation
Value
01H
02H
03H
04H
08H
09H
10H
20H
40H
80H
Error Condition
Illegal Function
Address Mark Not Found
Write Protect Error
Sector Not Found
DMA Overrun
Attempt to DMA Across a 64K Boundary
Bad CRC on Disk Read
Controller Failure
Seek Failure
Device Timeout, Device Failed to Respond