
DISK DRIVE OPERATION
6.4.1Check Power Mode (98h, E5h)
This command checks the power mode.
If the drive is in, going to, or recovering from the Standby Mode, the drive sets BSY, sets the Sector Count register to 00h, clears BSY, and generates an interrupt.
If the drive is in the Idle Mode, the drive sets BSY, sets the Sector Count register to FFh, clears BSY, and generates an interrupt.
6.4.2Download Micro Code (92h)
This command enables the host to alter the drive’s
6.4.3 Execute Device Diagnostics (90h)
This command performs the internal diagnostic tests implemented by the drive. The DRV bit is ignored. Both drives, if present, shall execute this command.
If Drive 1 is present:
•Drive 1 asserts PDIAG- within 5 seconds.
•Drive 0 waits up to 6 seconds for Drive 1 to assert
•If Drive 1 has not asserted
•Both drives execute diagnostics.
•If a Drive 1 diagnostic failure is detected when Drive 0 status is read, then Drive 1 status is obtained by setting the DRV bit, and reading status.
If there is no Drive 1 present:
•Drive 0 posts only its own diagnostic results.
•Drive 0 clears BSY, and generates an interrupt.
The Diagnostic Code written to the Error register is a unique
If Drive 1 fails diagnostics, Drive 0 "ORs" 80h with its own status and loads that code into the Error register. If Drive 1 passes diagnostics or there is no Drive 1 connected, Drive 0 "ORs" 00h with its own status and loads that code into the Error register.
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