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HP C1557A DDS 3 Autoloader




Jumpers & Switches


Apricot Part Number PT15904631
Vendor H.P.
Series DDS 3 AL
Model C1557A
Form Factor 5.25" HH
Height 3.2" / 82mm
Width 5.7" / 146mm
Length 8.0" / 203.2mm
Weight 4.8lbs / 2.2Kg
Tape Type DDS-3 125m 4mm DAT
Tape Length 125m
Capacity Native 6x12GB=72GB
Capacity Compressed @2:1 6x24GB=144GB
Recording Media MP++
Cartridge Size (W x D) 73 x 53mm
Flux Density 152,500 ftpi
Tracks 2,804 trks/inch


Transfer Rate, @ 2:1 Burst 2MB/s
Transfer Rate, Native Burst 1MB/s
Head to Tape Speed, Read / Write 236 ips
Search / Rewind 100x normal
Physical Interface SE 8bit SCSI
Logical Interface SCSI-2
Maximum Transfer Rate 5MB/s
Buffer Size 2MB
Hardware Compression Yes, DCLZ
Recording Method Helical Scan
Recording Code DDS-DC
Error Recovery Type Reed S'mon C3
Read after Write Verify Yes
Correctable Read Error Rate 1 in 104 bits
Uncorrectable Read Error Rate 1 in 1015 bits


Minimum Ambient operating Temperature 5C
Maximum Ambient operating Temperature 45C
Maximum Thermal Gradient 2C/minute
Average Power Consumption Combined
Operating Maximum 28W
Nominal Read / Write 9W
Nominal Idle 9W
DC Power Requirements Combined
+12V Peak 2.0Amps
+12V Operational Nominal 0.2Amps
+5V Peek 1.20Amps
+5V Stepping Head Nominal 1.20Amps
MTBF 55,000 poh

Jumpers & Switches


The SCSI ID is set using the jumpers on the set of pins beside the SCSI connector at the rear of the drive, shown below:

SCSI Jumper Pins

The three significant bits in the ID give a range of 0 to 7 as follows:

SCSI ID Bit 2 Bit 1 Bit 0
0 0 0 0
1 0 0 1
2 0 1 0
3 0 1 1
4 1 0 0
5 1 0 1
6 1 1 0
7 1 1 1

1 = shorted
0 = open

The drive reads the SCSI ID at power-up and during self-test.

Data Compression Control

Data compression can be controlled through the jumper pin shown above. The pin is only monitored at power-on, and controls whether data compression is enabled by default. Any subsequent change to the pin are ignored.

Pin State Effect
Unconnected This is the default. Data compression is controlled by the configuration switches 1 and 2 (on the underside of the drive) and through the SCSI MODE SELECT command.
Connected to 0V Data compression is disabled. The setting of configuration switch 1 is ignored. Switch 2 is valid. However, data compression can still be controlled through MODE SELECT. Note that when reading, the drive will always decompress compressed data

It follows from this that if you wish to use this pin, you should switch 1 on the underside of the drive to ON

Terminator Power

The drive will provide termination power for the SCSI termination resistors if a jumper is set across the two pins marked "Term power" as shown in the diagram

Configuration switches

There is a set of configuration switches on the underside of the drive, shown below:

With the drive switched off, use the information below to select the correct configuration for your system.

For the drive to operate correctly, appropriate drivers and application software must be loaded on the host computer.

Data Compression

Switches 1 and 2 are normally used to configure the way in which data compression is set for the drive. The following table shows the available options:

Switch 1 Switch 2 Meaning
On On Compression enabled at power-on with host control
On Off Compression enabled at power-on no host control
Off On Compression disabled at power-on. The host is allowed to control compression
Off Off Compression disabled at power-on no host control

When switch 1 is on, data written to the tape will be compressed without the knowledge of the host.

Media Recognition System (MRS)

Switch 3 is used to configure the drive to respond to DDS Media Recognition System tapes:

Switch 3 Meaning
On The Media Recognition System is disabled. All DDS tapes are treated the same, whether they posses the Media Recognition stripes or not.
Off The Media Recognition System is active. This is the default setting. Non Media Recognition System tapes are treated as if they are write-protected.

Switches 4 to 8

Switches 4 to 8 are used to specify connectivity and functionality according to host or customer requirements. The default settings for all switches is on.

Option switches

The autoloader option switches are on the rear-panel. The switches are read at power-on. When the autoloader is switched off, you can set the following configurations (other settings are not used at this time).

4 3 2 1 Value Auto-stack Auto-eject Allow Resequencing LUN 1 Magazine Ready LUN 0 Drive Inquiry
On Off Off On 1h Enabled Enabled      
Off On On On 6h (HP Series 800)     Enabled Enabled Enabled
Off On On On 7h (HP Series 700)     Enabled Enabled  
On On On On Fh (Default)          
Auto-stack The autoloader will enter Stacker mode after a magazine has been inserted, and the first cartridge will automatically be loaded.
Auto-eject When the autoloader is in Stacker mode it will eject the magazine after the last cartridge in the magazine is loaded.
Allow Resequencing While the autoloader is in Stacker mode, you can select another cartridge to be loaded into the drive by using the Select and Load buttons. When this option is not enabled, the Load and Select buttons are ignored in Stacker mode.
LUN 1 Magazine Ready A TEST UNIT READY command to LUN 1 will receive a NOT READY status message unless a magazine is present and magazine cencus data is available. When this option is not enabled, a TEST UNIT READY command will receive a GOOD status report whenever the autoloader has completed the power-on self-tests. This provides a method of detecting whether a magazine is present.
LUN 0 Drive Inquiry The product ID sent in response to an INQUIRY command to LUN 1 will be that of the embedded tape drive. When this option is not enabled the ID sent is that of the entire autoloader.


Computing for a Connected World