Host Adapter Command Overview - Adaptec AHA-1740A Technical Reference Manual

Chapter Five
Standard Mode Firmware Description

Host Adapter Command Overview

Standard Mode is the mode in which the AHA-1740A/1742A/1744 can operate in or-
der to run existing software for earlier Bus Master host adapters. In Standard Mode,
the AHA-1740A/1742A/1744 supports two types of commands: SCSI and adapter com-
mands. SCSI commands are issued using the mailbox protocol and a Command Con-
trol Block (CCB). When SCSI commands are used, the AHA-1740A/1742A/1744 is
operating in true multithreading mode. In this mode of operation, the AHA-
1740A/1742A/1744 is capable of executing multiple commands for multiple targets
concurrently. The AHA-1740A/1742A/1744 maximizes the I/O transaction through-
put by managing SCSI disconnection and reconnection.
Adapter commands are issued by writing to the Command/Data Out port and most
commands cannot be issued when there are outstanding SCSI commands. Adapter
commands are used to initialize the host adapter and to establish control conditions
within the host adapter. Adapter commands are also used to transmit the special pa-
rameters for communication between the BIOS and the host adapter for the execu-
tion of Interrupt 13 operations.
Following is a list of the adapter command operation codes (hex):
Code
00
01
02
03
04
05
06
07
08
09
0A
0B
0C
0D
10
11
1A
1B
1C
1D
1F
Command
No Operation
Mailbox Initialization
Start SCSI Command*
Start PC AT BIOS Command
Adapter Inquiry
Enable Mailbox Out Available Interrupt*
Set Selection Time Out
Set Bus-On Time
Set Bus-Off Time
Set Transfer Speed
Return Installed Devices
Return Configuration Data
Enable Target Mode
Return Setup Data
Initialize SCSI Subsystem
Return Firmware Checksum
Write Adapter Channel 2 Buffer
Read Adapter Channel 2 Buffer
Write Adapter FIFO Buffer
Read Adapter FIFO Buffer
Echo Command Data
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