Avago Technologies LSI53C896 - Manual (Page 232)

5-4 SCSI SCRIPTS Instruction Set
Version 3.3 Copyright © 1998–2003 by LSI Logic Corporation. All rights reserved.
interrupts the host CPU and waits for further servicing by the host
system. It can execute independent Block Move instructions specifying
new byte counts and starting locations in main memory. In this manner,
the LSI53C896 performs scatter/gather operations on data without
requiring help from the host program, generating a host interrupt, or
programming of an external DMA controller. An overview of this process
is presented in
Figure 5.1 .
Figure 5.1 SCRIPTS Overview
System Processor
System Memory
(or Internal RAM)
SCSI Initiator Write Example
select ATN0, alt_addr
move 1, identify_msg_buf, when MSG_OUT
move 6, cmd_buf, when CMD
move 512, data_buf, when DATA_OUT
move 1, stat_in_buf, when STATUS
move 1, msg_in_buf, when MSG_IN
move SCNTL2 & 7F to SCNTL2
clear ACK
wait disconnect alt2
int 10
Data Structure
Message Buffer
Command Buffer
Data Buffer
Status Buffer
LSI53C896
SCSI
Bus
Write DSP
Fetch
SCRIPTS
Data
(Data is not fetched across system bus if
internal RAM is enabled.)
System
Bus