Commodore 1581 - Chapter 8: Machine Language Programs; Disk-Related Kernal Subroutines; Chapter 9: Burst Commands; CMD 1: Read

CHAPTER 9
BURST COMMANDS
The Burst Command Instruction Set (BCIS) is a series of power
ful, versatile, and complex commands that enables the user to format,
read, and write in numerous formats. Burst commands are sent via
kernal calls, but the handshaking of data is done by the user for
maximum performance. There is no parameter checking, so exercise
care when using the BCIS. For instance, if a burst read with an illegal
track address is sent to a 1581, the drive will keep trying to find the
invalid track. Reading and writing in other formats is automatic if the
commands are given in proper sequence. Please become thoroughly
familiar with all the commands and follow the examples given in this
chapter. It's important to follow the handshake conventions exactly for
maximum performance.
With the exception of READ and WRITE, burst commands do not
translate from logical to physical track and sector. All track and sector
parameters refer to physical locations (see Chapter 10). Burst sector
READ and WRITE commands provide a flag to enable logical to phys
ical translation. If the flag is set, the drive does the translation and the
default logical number of bytes per sector (256) is transferred instead
of the physical number of bytes per sector (512).
CMDl—READ
BYTE
00
01
02
03
04
05
06
BIT 7
0
0
L
6
1
0
E
5 4 3
0 1 0
1 1 0
X S 0
DESTINATION TRACK
DESTINATION SECTOR
NUMBER OF SECTORS
NEXT TRACK (OPTIONAL)
2
1
0
0
1
0
0
0
0
1
0
N
RANGE: All values are determined by the particular disk format and format of transla
tion table.
SWITCHES: L—logical flag (1 = do logical to physical translation)
E—ignore error (1 = ignore)
S—side select
N—drive number
PROTOCOL: Burst handshake
CONVENTIONS: Before you can READ or WRITE to a diskette, it must be logged-in
using either the INQUIRE DISK or QUERY DISK FORMAT command
(both are described later). This must be done once each time you
change diskettes.
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