| 
 | 
 
 | 
| Pin | 
Signal | 
Direction for host | 
Description | 
| 1                     RES | 
Out | 
Bus Reset signal | 
| 3,5,7,9,11,13,15,17 | 
DATA BUS | 
Bi-directional | 
Used for transferring Status, Data and Control information. | 
| 19                     GND* | 
 | 
Ground | 
| 20                     Key | 
 | 
An unused pin, which is clipped off at the drive to prevent incorrect cable attachment. | 
| 21                     AEN | 
Out | 
Host address enable, which is asserted during a DMA* cycle to disable the decoding of I/O port addresses. | 
| 23                     /IOW | 
Out | 
Host I/O write signal for writing data to an I/O port address. | 
| 25                     /IOR | 
Out | 
Host I/O read signal for reading data from an I/O port address. | 
| 27                     /DACK | 
Out | 
DMA* acknowledge signal asserted in response to the DMA* Request signal. This signal enables DMA* data transfer when either /IOR or /IOW signals are active. | 
| 29                     DRQ | 
In | 
DMA* Request asserted by the drive to initiate a DMA* transfer. | 
| 31                     IRQ | 
In | 
Interupt Request asserted by the drive to cause an interrupt to the host. | 
| 33,35                   SA1,SA0 | 
Out | 
Host I/O address lines 0 and 1 for selecting the drive's I/O ports. | 
| 37                     /CS | 
Out | 
Card Select signal asserted by the host to address the drive's I/O ports. | 
| 39                     /ACTIVE | 
In | 
Drive Activity signal asserted by the drive when it is processing a command.  Can be used to drive an external LED indicator. |