ZiLOG System 8000 Hardware Reference Manual

HRM 21 Zilog
APPENDIX B
WINCHES1'ER
DISK CON'TROLLER COMMANDS
HRM 21
B .. 1. General
Appendix C describes all the commands that the host CPU
sends to the controller through the command registers. Each
de~cription indentifies the registers that the host CPU
uses. Bits 0 through 4 of the command byte form the com-
mand field. Refer to Section 4 for additional iiformation.
The term CP (Command Port) means command register as used in
Section 4. For example, CPO is command register xxOO and
CP1 is command register xx01.
B .. 2. Format / UNIT /
The controller formats an entire disk drive with a single
controller command. The CPU sends the FORMAT command to the
controller by writing the unit number of the drive to be
formatted as CP1 and by issuing the Format command to the
.command port, CPO. Format writes the data field of each
sector with a pattern of alternating ones and zeros (OAA
hexadecimal) and rewrites each sector's header. After for-
matting the target unit, the entire format is read back and
the header field of each sector is validated. If an invalid
header is found, the Unrecoverable Error bit in the opera-
tion ending status byte is set, together with the Verify
Failure bit in the Operation Error Status Byte.
I UNIT I Unit is written to the controller through CP1. Any
value between zero and three is valid.
B.3. Read Sector
/ UNIT I HEAD I CYLINDER I SECTOR I WORD COUNT I ADDRESS
The Read Sector command requires both a disk address [unit,
head, .cylinder, sector] and a host system buffer address
[word count, address]. Less than one sector of information
is transferred if the word count is less than a sector (512
bytes) in length. The controller command for multiple sec-
tor reads and single sector reads is equivalent with the
word count determining the number of sectors for the
transfer.
B-1
Zilog
B-1

ZiLOG System 8000 Specifications

General

Brand	ZiLOG
Model	System 8000
Category	Desktop
Language	English