Tandy 1400LT Service Manual page 233

READY
A "Low" level on this line indicates that the drive is ready.
The READY signal becomes "Low" when all of the following conditions are satisfied.
(1) The drive is selected.
(2) A cartridge is correctly loaded.
(3) Vcc is 4.2V min.
(4) Two INDEX pulses are generated after the INDEX cycle is fixed.
The READY signal becomes "Low", a maximum of 1 sec after the Spindle Motor starts to run.
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