Set Selection Time out (Operation Code 06)This command sets the SCSI selection time out value. The SCSI Selection time outvalue is used to determine whether a SCSI selection was successful. If the SCSI BSYsignal is not returned within the specified time out value, the selection will be termi-nated and an appropriate error message posted with the returned CCB. This com-mand expects four outbound data bytes to be provided as defined below:Byte Description00 Enable/Disable Selection Time OutThis parameter byte specifies whether the selection time out will be used. If thebyte is set to 00h, no time out will be performed. If the byte is set to 01h, the timespecified in bytes 02 and 03 will be used as the selection time out by the SCSI. Thedefault value established by the reset process is 01h, indicating the time out isenabled.01 Reserved (00)This byte must be zero.02 Time Out Value (MSB)This two-byte value specifies the time in milliseconds that will be used for theselection time out. The default value is 250 milliseconds03 Time Out Value (LSB)This two-byte value specifies the time in milliseconds that will be used for theselection time out. The default value is 250 millisecondsAfter completing this command, HACC will be asserted, indicating normal comple-tion. INVDCMD will be asserted if the data byte 0 is neither 00 nor 01 or if byte 1 isnot zero, indicating an invalid command.Set Bus On Time (Operation Code 07)NoteThis command is not used by the AHA-1740A/1742A/1744 but is supported in orderto be compatible with software written for earlier host adapters, such as the AHA-1542B.This command specifies the time that the host adapter spends on the bus when trans-ferring data. The bus on duration is adjustable from 2 to 15 microseconds. The de-fault setting is 11 microseconds. One data byte is passed out to the host adapter toindicate the bus on duration in microseconds.Byte 0 Bus On Time (2 to 15 microsecondss)After completing this command, HACC will be asserted indicating normal comple-tion. INVDCMD will be asserted, indicating an invalid command, if the data byte isgreater than 15. The valid range is 2 to 15 decimal. Due to the internal differences be-tween the AHA-1740A/1742A/1744 and earlier host adapters, the data is not actuallyused but is saved and returned in the Return Setup Data command. The command isaccepted only for compatibility.EISA-to-Fast SCSI Host Adapter Standard Mode Firmware Description5-5
