"IDE - hardware reference & information document" - читать интересную книгу автора (Ivopol A.)

slave does not generate SPSYNC and must be responsible to
synchronize its index to SPSYNC. If a drive does not support
synchronization, it will ignore SPSYNC. In the event that a
previously synchronized drive loses synchronization, it does
not clear DRDY.

Prior to the introduction of this standard, this signal was
defined as ALE (Address Latch Enable) and was used for an
address valid indication from the host system. If used, the
host address and chip selects, ADDR0 through ADDR2, CS1FX- and
CS3FX- were valid at the negation of this signal and remained
valid while ALE was negated, therefore the drive did not need
to latch these signals with ALE.

INTRQ
is used to interrupt the host system when the drive has a
pending interrupt, the drive is selected and the host has
enabled drive interrupts by clearing nIEN in the Device Control
Register.

INTRQ is negated by:

+ assertion of -RESET.
+ the setting of SRST in the Device Control Register.
+ the host writing to the Command Register.
+ the host reading the Status Register.

NOTE: Some drives may negate INTRQ on PIO data transfer
completion, except on a single sector read or on the last
sector of a multi-sector read. On PIO transfers INTRQ is
asserted at the begining of each data block to be transfered. A
data block is usually a single sector except when declared
otherwise via the Set Multiple Command. An exception occurs on
Format Track, Write Sector(s), Write Buffer and Write Long
commands and INTRQ will not be asserted at the begining of the
first data block to be transferred.

-IOCS16
indicates to the host that the 16 bit data port has been
addressed and the drive is prepared to send/receive a 16 bit
data word. This signal is an open collector output. D8...D15
are only valid when -IOCS16 is active and the drive is
transferring data. The transfer of ECC data occurs only on
D0...D7 so D8...D15 are invalid during ECC transfers.

ADDR0-2
used to select a register or a data port in the drive.

-PDIAG
will be asserted by Drive 1 to indicate to Drive 0 that it has