HP 7957A Hardware Manual page 18

Interface Information
7957 A/7958A
BIT
POSITION
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
o
Table 2-1. General Configuration Response Bits
DRIVE FEATURE
Tape Drive
Format Speed Tolerance Gap Required
Track Offset Option Implemented
Data Strobe Offset Option Implemented
Rotational Speed Tolerance> 0.5%
Transfer Rate> 10 MHz
Transfer Rate> 5 MHz <= 10 MHz
Transfer Rate <= 5 MHz
Removable Cartridge Drive
Fixed Media Drive
Spindle Motor Control Option Implemented
Head Switch Time> 15 usec
RLL Encoded (not MFM)
Controller Soft Sectored (Address Mark)
Drive Hard Sectored (Sector Pulses)
Controller Hard Sectored (Byte Clock)
* 1 indicates that drive implements specified feature.
BIT
VALUE*
o
o
1
1
o
o
1
o
o
1
1
o
1
o
1
o
If the controller attempts a write with an in-
valid head selected, the drive responds by set-
ting A TTENTION and Invalid Or
Unimplemented Command status bit. If the
controller attempts to read with an invalid
head, the read will be executed with the last
valid head selected.
• WRITE GATE. The WRITE GATE timing
used during formatting and normal writing is
shown in figures 2-2 and 2-3, respectively.
• HEAD SELECT LINES. When selecting a
head, the controller must ensure that all head
select lines change within less than 100
nanoseconds. This avoids an inadvertent head
selection during transition of the head select
lines. Valid head select values for each drive
are shown in table 2-4.
2-2
The following timing restrictions apply to the
WRITE GATE signal:
- When the drive performs a head switch opera-
tion, the controller must not activate WRITE
GATE until COMMAND COMPLETE is ac-
tivated, indicating completion of the head
switch.
- When performing a write following a read,
WRITE GATE must not be activated for a min-
imum of 500 nanoseconds after READ GATE
is deactivated.