Viper 60s Theory Of Operation And Maintenance Manual page 132

6.1 Overview
CHAPTER 6
THEORY OF OPERATION
THEORY OF OPERA TION
Viper SCSI drives feature LSI circuitry and surface-mount technology and conform to ANSI
X3.131 and QIC-02 standards. The Viper drive consists of multiple mechanical subassemblies,
two electrical assemblies (PCBs), and a front bezeL All are assembled in a half-high, 51 /4-inch
drive chassis configured to fit inside a standard half-high floppy disk slot. Figure 6-1 is a
simplified block diagram of the Viper drive. Drive electronics are located on the Main PCB
and the Motor Driver PCB.
The Viper drive main PCB contains electronics for drive operations and interface. This single
multilayer PCB offers advanced LSI circuitry and surface mount technology to provide high
data reliability and low power consumption.
The motor driver PCB is mounted in the back of the drive behind the cartridge loading area
and contains LSI circuits to control the speed and direction of the capstan drive motor.
SCSI control signals are transmitted to and from the Viper via the host interface connector at
the rear of the drive. Power is received through a 4-pin connector located at the rear of the
drive.
6.2 Printed Circuit Board
Under firmware program direction by the 64 Kbyte EPROM, the Intel8-bit 8031 microproces-
sor provides complete control over the operation of the Viper drive. The microprocessor
together with the VLSI automatically formats the data as it is written onto tape.
All read/write registers for transfer of data blocks within the drive electronics reside in VLSI
and a 64 kilobyte buffer with parity. The data blocks are extracted from the formatted data as
they are read from tape and sent to the host through the SCSI interface. Circuits for writing
data to and reading data from tape are provided on the SCSI bus controller with all address-
ing control processed on the VLSI. The microprocessor and VLSI perform all error recovery
operations.
6-1