Seagate ST251 Product Manual page 7

2.2 DRIVE SELECT
The Drive Select line enables the controller to select and address the
drive. Control cable interface options may use either a daisy-chain or
radial configuration.
Pins 15-16 shorted enables Drive Select 1
Pins 13-14 shorted enables Drive Select 2
Pins 11-12 shorted enables Drive Select 3
Pins 9-10 shorted enables Drive Select 4
2.2.1 DAISY-CHAIN/RADIAL DRIVE CONFIGURATIONS
The ST251/251R/277R can be configured in either a daisy-chain or
radial mode. The radial option is enabled by shorting pins 1 and 2 at
J7. The resistor termination pack must remain installed on
any
radially
configured drive.
In a daisy-chain configuration, the last drive in a chain must have the
resistor termination pack installed.
2.3 WRITE FAULT LATCH OPTIONS: JP1 AND J7
These options allow the user to configure the Write Fault reset to spe-
cific system requirements.
JP1 has three jumper pads, and is located adjacent to the 34-pin J1
connector. Figure 7 on page 2-1 illustrates JP1 and indicates pin-1. J7
is located midway between the PCB edge-connectors (see "2.1 Drive
Configuration Shunt J7" on page 2-1).
STANDARD: 1 and 2 jumpered on JP1
Write Fault will be cleared when Write Gate is false. A Write Fault will
only occur when Write Gate is true.
LATCHED: 2 and 3 jumpered on JP1
This option will maintain Write Fault true after Write Gate goes false
and is recommended for controllers that do not edge-detect Write Fault.
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INTRODUCTION
This manual supports the ST251/251 R/277R disc drives. It supercedes
and replaces the ST251 Product Manual, 36016-001, Rev. B.
2-2
ST251/251 R/277R Product Manual, Rev.A
ST251/251R/277R Product Manual, Rev.A
vii