Seagate SCSI Interface Product Manual page 53

SCSI Interface Product Manual, Rev. J
If the last data byte transferred for a command does not fall on the DB(15-8,P1) signals for a 16-bit wide trans-
fer, then the values of the remaining higher-numbered bits are undefined. However, parity bits for these unde-
fined bytes shall be valid for whatever data is placed on the bus.
Ignore Wide Residue message (23h)
The Ignore Wide Residue message is not an extended message, but it is placed here in context with the 16-bit
Wide Data Transfer message, since it applies when the 16-bit wide data transfer capability is used.
Table 10. Ignore Wide Residue message format
Bit 7
Byte
0
1
The Ignore Wide Residue message (Table 10) shall be sent from a target to indicate that the number of valid
bytes sent during the last REQ/ACK handshake of a Data In phase is less than the negotiated transfer width.
The ignore field indicates the number of invalid data bytes transferred. This message shall be sent immediately
following that Data In phase and prior to any other messages. The ignore field is defined in Table 11.
Note. More than one Ignore Wide Residue message may occur during an I/O process.
Table 11: Ignore field definition
Invalid data bits
Ignore 16-bit transfers
00h Reserved
01h DB(15-8)
02h Reserved
03h Reserved
04h–FFh Reserved
Even though a byte is invalid its corresponding parity bit shall be valid for the value transferred.
6 5
Message Code (23h)
Ignore (01h, 02h, 03h)
4 3 2 1
39
0