IBM B-Series, Maintenance Information

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Drive Logic Card Overview
The drive logic card, item
2
, contains the primary electronic controls for the drive and the library device,
if installed. It is plugged into the mother board, item
11
, and is the first card visible when the top
protective cover of the drive is removed. This card contains the SCSI controls for the box, several
processors, memory buffers, clock generation circuits, and control logic for R/W data flow and reel to reel
tape motion. It provides connectivity for the library function through the library control card.
Drive Logic Card—How it works
The drive logic card, located in each drive pack, basically consists of a data path and a control path. The
data path receives data from the SCSI bus, then buffers it, checks it for parity and CRC, compacts it,
re-buffers it, formats it to fit the 3570 data format, and sends it to the drive analog card, and ultimately to
the head-actuator assembly to be written to the media. In read-back, it receives read data pulses from the
drive analog card, clocks them, de-skews them, corrects parallel data, buffers it, de-compacts it, and
transfers the data to the SCSI bus.
The drive logic card contains the main microprocessor, the microcode load, clock generation circuits, reset
controls, and control registers that interface with all other drive electrical/mechanical components.
Library Models:
The drive logic card controls the motion of the accessor assembly and the picker
assembly by sending commands to these devices through the library control card which performs as the
library interface. The drive logic card also monitors tach pulses from the motors, and sense data from the
various library sensors through the library control card interface.
Host Communications:
The drive logic card serves as the primary SCSI interface for the device
through a SCSI adapter and on-board SCSI drivers. All host communications to the 3570 go through the
drive logic card via this interface. SCSI commands are received, and routed under microcode control
throughout the device. SCSI data is received and sent as discussed earlier.
The SCSI ID switch is located on the drive logic card and is used to set the SCSI address for drive-only
installations. The SCSI ID switch is not used on library models. The SCSI address on library models is set
from the library operator panel display.
Microcode:
Microcode, which is housed on the drive logic card, handles data and commands from the
SCSI bus, and transfers data and controls the drive analog card, drive servo card, the loader assembly,
head-actuator assembly, and the library components. During read from the media, the microcode controls
the receiving and buffering of data from the drive logic card, and controls the actuator location in relation
to the media. The microcode also provides communication to the operator or CE by communicating
through the drive LEDs, the library operator panel display, and library LEDs. Bring-up diagnostics perform
initialization and testing during Power On, and collects and presents error or ATTENTION data when
intervention is required. Each installed drive contains microcode.
Data Handling:
The drive logic card controls special compaction hardware to compact data before
sending it out to be written to the tape media. During a tape read operation, data that is received from the
R/W head is first corrected for skew, then is un-compacted and buffered for further transmission over the
SCSI bus.
Sense Gathering:
Sensing devices located in the drive pack send sense data through the drive
servo card to the drive logic card. Sensing devices located in the library area send sense data through the
library control card to the drive logic card.
INTRO-20
IBM 3570 MI