Table of Contents
Advertisement
When the host computer responds with MESSAGE REJECT message to
SYNCHRONOUS DATA TRANSFER REQUEST message from the controller or
when the host computer can not receive the message successfully ( message
parity error ), the negotiation is canceled and the controller goes to Asynchronous
data transfer mode.
Note : The negotiation is agreed if the host computer responded with ABORT
message .
Precautions on the host computer side
The transfer period of synchronous data transfer is based on the transfer
capability of SCSI bus and it is not limited by transfer capability of DMA.
The shortage of DMA transfer capability is accommodated by REQ / ACK offset
( Max. No. of REQ pulses that may be sent prior to receipt of corresponding ACK
pulses.).
After REQ / ACK offset value reaches to the maximum, it is avoided to transmit
the next REQ signals until ACK signals are received.
Wide Data Transfer Request (010203XX
Byte
The WIDE DATA TRANSFER REQUEST message is sent from the host
computer to the controller to establish the width of the data path to be used for
DATA transfer phases ( applicable to DATA IN and DATA OUT phases only ).
Table 3.4 shows wide data transfer request. Extended message length is
specified the number of bytes transferred following this length (It does not
include itself).
The code 03
The value responded by the controller corresponding to the TRANSFER
WIDTH EXPONENTS(XX
3.5.
3 SCSI BUS
Table 3.4 WIDE DATA TRANSFER REQUEST
Value
0
01
H
1
02
H
2
03
WIDE DATA TRANSFER REQUEST
H
3
XX
H
in byte 2 indicates WIDE DATA TRANSFER REQUEST message.
H
) specified from the host computer is shown in Table
H
)
(Only for wide SCSI drive)
H
Description
Extended message
Extended message length
code
Transfer width exponent
OEM MANUAL:K6602924
Revision: 1 / Date: 2003.03.06
Page: 44 / 273
Advertisement
Table of Contents
