IBM B-Series, Maintenance Information

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Drive Logic Card to Drive Analog Card Interface:
Most clocking for the 3570 is generated
by the drive logic card. It operates at 40Mhz or clocks derived from this frequency. The microprocessor
resident on the drive logic card runs at 20Mhz. The only off card use for drive logic card clock circuitry is a
20Mhz signal sent to the drive analog card during write operations and during transfer of LWR (Loop Write
to Read) data. The library control card contains its own clock controls. During a write operation the drive
logic card sends equalized write data and clock pulses to the drive analog card. During transfer of LWR
data, the drive logic card clocks the LWR data from the drive analog card. The data is buffered and
checked in both directions to ensure data integrity.
Drive Logic Card to Drive Servo Card Interface:
The drive logic card is also the primary
electronic source for controlling movement of the reel-to-reel motors, the head actuator, and readout of the
loader sensors. The drive logic card provides control registers for each of these functions, which in turn
are powered by the drive servo card to perform the actual movement of motors and solenoids. Feedback
of tach pulses and sensors is transferred to the drive logic card from the drive servo card for processing
by the microcode.
Reset and Power Controls:
Power on reset for the 3570 is handled by the drive logic card. It
checks power as it comes up or goes down, and provides reset levels to the other electronic circuits until
power is at the proper levels. This
clamping of the electronic cards keeps noise and glitches from
occurring during power transitions.
Drive Analog Card
The drive analog card, item
4
, contains the write drivers, read preamplifiers and bias circuits for both
data and servo channels. It provides precise switching of write current for four channels at a time to the
R/W head during a write cycle, and detects and converts analog signals from the R/W head to digital
signals during a tape read cycle. The drive analog card is designed and positioned so that it makes
physical contact with the R/W head through thin film cable connections, item
5
, yet can still be plugged
into the mother board. The R/W head is part of the head-actuator assembly, item
1
.
Head-Actuator Assembly
The head-actuator assembly, item
1
, contains the R/W head, and the actuator assembly, factory
pinned. The entire unit is one FRU. The R/W head transfers write current as controlled by the drive analog
card to the tape as it passes in contact with the R/W head during a write cycle, and transfers signals from
the tape as it passes in contact with the R/W head during read cycles. The actuator assembly positions
the head in the appropriate location to read or write across the width of the tape.
Drive Servo Card
The drive servo card, item
8
provides circuitry that drives the loader motor, reel motors, and head
actuator from signals originating in the drive logic card. It is the last card in the stack to plug into the
mother board.
Loader Assembly
The loader assembly, item
12
, is mounted on the bottom plate, item
9
. The loader assembly contains
the mechanical and electrical components to move the tape cartridge into and out of the loader, to move
the tape forward and backwards, to sense when the tape cartridge is in position to be read, and to sense
the type of tape cartridge that is loaded. The loader assembly as attached to the bottom plate is one FRU.
There are several smaller FRUs such as the loader door, drive LED card and the loader home sensor that
INTRO
Introduction
INTRO-21