Difference between revisions of "Floppy Disk Drive Cable Termination and Device Addressing"
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Latest revision as of 11:11, 21 April 2021
Cable Termination
Similar to the SCSI interface, the standard IBM PC floppy disk drive bus needs termination at each end, which is achieved by fitting a 150-ohm resistor network to a socket provided on the last drive on the cable (and similarly on the controller card) such as the Beckman 899-3-R150.
Device Addressing
The IBM PC floppy disk drive bus includes the facility for up to four drives to be daisy-chained, with device addressing being controller by pins 6, 10, 12 and 14. Initially, jumpers were used to manually select the device ID (0 through 3) with a flat ribbon cable.
Another option is a 'twisted' ribbon cable, where the cables serving pins 6 to 14 are reverse between the first and sector drive connector, thereby providing 'cable select' addressing for two devices (only). Using this method, both drives should be jumpered to drive 1 (DS1), with the drive connected to the first (untwisted) connector being drive 1, and the drive connected to the second (twisted) connector being drive 0 (DS0).