Compaq Deskpro EP 6233 Technical Reference Manual page 109

Command Register, I/O Port 1F7h/177h (Write Only)
The IDE controller commands are written to this register. The command write action should be
prefaced with the loading of data into the appropriate registers. Execution begins when the
command is written to 1F7h/177h. Table 5-4 lists the standard IDE commands.
Table 5–4. IDE Controller Commands
Table 5-4.
IDE Controller Commands
Command
Initialize Drive Parameters
Seek
Recalibrate
Read Sectors with Retries
Read Long with Retries
Write Sectors with Retries
Write Long with Retries
Verify Sectors with Retries
Format Track
Execute Controller Diagnostic
Idle
Idle Immediate
Enter Low Power and Enable/Disable Timeout
Enter Idle and Enable/Disable Timeout
Check Status
Identify
Read Buffer
Write Buffer
NOP
Read DMA with Retry
Read DMA without Retry
Read Multiple
Set Features
Set Multiple Mode
Sleep
Standby
Standby Immediate
Write DMA with Retry
Write DMA without Retry
Write Multiple
Write Same
Write Verify
* Without retries, add one to the value.
Alternate Status Register, I/O Port 3F6h/376h (Read Only)
The alternate Status register at location 3F6h holds the same status data as location 1F7h but
does not clear hardware conditions when read.
Value
91h
7xh
1xh
20h*
22h*
30h*
32h*
40h
50h
90h
97h, E3h
95h, E1h
96h
97h
98h
ECh
E4h
E8h
00h
C8h
C9h
C4h
EFh
C6h
99h, E6h
96h, E2h
94h, E0h
CAh
CBh
C5h
E9h
3Ch
Compaq Deskpro EP Series of Personal Computers
First Edition - April 1998
Technical Reference Guide
5-7