8 bit IDE interface

 There is a possibility to make IDE hard disk interface much simpler. Main complication by projecting 16-bit interface was 16/8 bit data transfer between Z80 CPU and IDE hard disk.

 Using only lower 8 data bits of hard disk will halving it's capacity, but by larger hard disks it should be not problem, because there is no so much Spectrum software - to fill, lets say 1 GB space. In this case interface can be made with only one chip:


IDE hard disk lines D8-D15 stay unconnected, line /SELS goes to Vcc (+5V), and this is all with hardware.

TUP - any low power PNP silicon transistor. E.g. BC327, BC212.

Position of pins on connectors you may find on 16 bit interface scheme .

I/O addresses for this solution:

Data register : #2B

Parameter reg.: #2F

Sector count r.: #6B

Start sector r.: #6F

Cylinder low : #AB

Cylinder high : #AF

Head reg. : #EB

Command/status: #EF

Example routines for multiple sector read/write for this interface are in : 8-bit programming reference .