Enhanced Small Device Interface [ESDI] is a Hard Disk Drive [HDD] interface used in the 1980's and 90's.
ESDI was rendered out-dated by the introduction of the ATA disk drive interface [IDE].
ESDI had a data rate of 20M Bytes/sec over a 20-pin cable. The data cable and control cable pinout is shown below.
ESDI Status: Withdrawn;
This disk drive interface standard was originally published as X3.170-1990.
In 1991, an amendment was approved and the combined documents were identified as X3.170:1990/X3.170a-1991.
In 1994, ESDI was reaffirmed as X3.170-1990[1994]/X3.170a-1991[1994]. This standard was withdrawn in April 1999.
| GROUND | 1 | 2 | ~HD SLCT 3 |
| 3 | 4 | ~HD SLCT 2 | |
| 5 | 6 | ~WRITE GATE | |
| 7 | 8 | ~CNFG/STATUS | |
| 9 | 10 | ~XFER ACK | |
| 11 | 12 | ~ATTENTION | |
| 13 | 14 | ~HD SLCT 1 | |
| Key (no pin) | 15 | 16 | ~SECTOR |
| GROUND | 17 | 18 | ~HD SLCT 1 |
| 19 | 20 | ~INDEX | |
| 21 | 22 | ~READY | |
| 23 | 24 | ~XFER REQ | |
| 25 | 26 | ~DRV SLCT 0 | |
| 27 | 28 | ~DRV SLCT 1 | |
| 29 | 30 | Reserved | |
| 31 | 32 | ~READ GATE | |
| 33 | 34 | ~CMD DATA |
| ~DRV SLCTD | 1 | 2 | ~SECTOR |
| ~CMD COMPL | 3 | 4 | ~ADDR MK EN |
| GROUND | 5 | 6 | GROUND |
| +WRITE CLK | 7 | 8 | -WRITE CLK |
| GROUND | 9 | 10 | +RD/REF CLK |
| -RD/REF CLK | 11 | 12 | GROUND |
| +NRZ WRITE | 13 | 14 | -NRZ WRITE |
| GROUND | 15 | 16 | GROUND |
| +NRZ READ | 17 | 18 | -NRZ READ |
| GROUND | 19 | 20 | ~INDEX |
As the ESDI standard was withdrawn in 1994, there is no specification to follow.
Working a design to a non-existent standard is never a good idea.
So not only is this standard out-dated, the entire interface is obsolete.
Obviously you should not design to an out-dated standard.
No related IC manufacturers or components are listed here because the interface is obsolete.
However the signal assignments are still valid if you happen to have a hard drive in need of debug.
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