Fiber Optic Wiki

RTU in RFTSs and Full-feature OTDR

August 5, 2011

The equipment is summarized below, and detailed in GR-196, Generic Requirements for Optical Time Domain Reflectometer (OTDR) Type Equipment.

Multiple devices on a cable

August 4, 2011

If two devices attach to a single cable, one must be designated as device 0 (commonly referred to as master) and the other as device 1 (slave). This distinction is necessary to allow both drives to share the cable without conflict. The master drive is the drive that usually appears "first" to the computer's BIOS and/or operating system. On old BIOSes (Intel 486 era and older), the drives are often referred to by the BIOS as "C" for the master and "D" for the slave following the way DOS would refer to the active primary partitions on each.

Differences between connectors on 80-conductor cables

August 4, 2011

The image shows PATA connectors after removal of strain relief, cover, and cable. Pin one is at bottom left of the connectors, pin 2 is top left, etc., except that the lower image of the blue connector shows the view from the opposite side, and pin one is at top right.

Parallel ATA interface

August 4, 2011

Parallel ATA cables transfer data 16 bits at a time. The traditional cable uses 40-pin connectors attached to a ribbon cable. Each cable has two or three connectors, one of which plugs into an adapter interfacing with the rest of the computer system. The remaining connector(s) plug into drives.

Obsolescence of ATA

August 4, 2011

For a long period of time, ATA ruled as the primary storage device interface and in some systems a third and fourth motherboard interface was provided (for example, Promise Ultra-100), for up to eight ATA devices attached to the motherboard.

Interface size limitations

August 4, 2011

Due to lack of foresight the first drive interface used 22-bit addressing mode which resulted in a maximum drive capacity of 2 GByte. Later the first formalized ATA specification used a 28-bit addressing mode, allowing for the addressing of 228 268 435 456 sectors (blocks) of 512 bytes each, resulting in a maximum capacity of 128 GiB (137 GB).

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