Power On/Off Sequencing; 3803 Model 2 Features; Nine-Track Nrzi; Seven-Track - IBM 3803 Manual

Power On/Off Sequencing
3803 Model 2 Features
Nine-Track NRZI
Seven-Trac.k
System power interlock circuits control normal power on/ power off sequencing
for the 3803/3420 tape subsystem. However, maintenance activities may
necessitate dropping power in the tape control.
Features available on a 3803 Model 2 are Nine-Track
NRZI,
Seven-Track,
Two-Channel Switch, and Device Switch. See Figures 3, 4, and 5.
The nine-track
NRZI
feature, available on the 3803 Model 2, permits operation in
nine-track
NRZI
mode. Nine-track
NRZI
operation requires a 3420 Model 3, 5, or
7 tape unit with the dual density feature. Operation of this feature is similar to
that of the 3803-1 with the dual density feature.
The seven-track feature permits operation in seven-track
NRZI
mode in addition
to the nine-track operation provided by the nine-track
NRZI
feature. Seven-track
operation with a 3803 Model 2 is at 800/556/200
BPI.
The seven-track feature
contains both the data translator and data converter for seven-track operations.
Their operation is similar to that of the 3803 Model 1 with the seven-track
feature. For seven-track operation, the seven-track feature on a 3420 Model 3,
5, or 7 and on the 3803 Model 2 are required. The nine-track
NRZI
feature is a
prerequisite for the seven-track feature on the 3803 Model 2.
Writing a tape with the translator on causes eight-bit bytes from the 1/0 interface
to be written on tape as six-bit
BCD
characters; reading such a tape causes six-bit
BCD
characters to be translated into their
EBCDIC
equivalents. When using the
translator, data rates are not changed and there are no changes in the tape unit's
operation.
Writing a tape with the data converter on causes four tape characters (24 bits) to
be written for every three storage bytes (24 bits); reading such a tape reverses
the process by converting four tape characters into three storage bytes. Data
conversion reduces the data transfer rate to 7 5 % of the operating rate with data
converter off.
Density (BPI) 3803-2 3420-3/5/7 3420-4/6/8
(Note 1) (Note 4) (Notes 2, 4) (Note 3)
6250, 9-Track Standard N/A 6250 Feature
1600, 9-Track
Standard 1600 Feature 6250/1600 Feature
800, 9-Track 9-Track NRZI Feature Dual Density Feature
N/A
800, 7-Track
7-Track Feature 7-Track Feature N/A
556, 7-Track 7-Track Feature 7-Track Feature
N/A
200, 7-Track 7-Track Feature 7-Track Feature N/A
Notes:
1. Density must be specified for each nine-track 3420 tape unit.
2. 3420-3/5/7 can be attached to 3_803-1 or 3803-2.
3. 3420-4/6/8 can be attached to 3803-2 only.
4. 9-Track NRZI feature is a prerequisite for 7-Track feature on 3803-2.
Figure 3. Density Feature Combinations
Section 1: Introduction
15