Hi

I have designed an IDe interface by directly using 8051 I/O ports. The hard disk doesn't seem to respond to any of the IDE commands send to the disk's controller.

Port 1 of the 8051 is connected to the control pins and port 2 and 3 are connected to Data bus low and high respectively. The Sample program given below is supposed to do a software reset. However, the hard disk doesn't seem to respond. What could be the problem?

Port 1 interface:

|\
P1.7 -------| \.----- *RESET
|/

|\
P1.6 -------| \.----- *DIOR
|/

|\
P1.5 -------| \.----- *DIOW
|/


|\
P1.4 -------| \.----- *CS1
|/


|\
P1.3 -------| \.----- *CS0
|/



P1.2 ---------------- DA2



P1.1 ---------------- DA1



P1.0 ---------------- DA0


SAMPLE PROGRAM:
ORG 0000H
MOV P3,#00000000B
MOV P2,#00000100B ;set SRST bit in the device control register

MOV A,#00010110B ;select the device control register

MOV P1,A
ORL A,#00100000B ;assert the write strobe

MOV P1,A
MOV R1,#250
Loop: DJNZ R1,Loop ;generate a short delay

CLR A
MOV P1,A ;clear the control signal

END

regards
chanda