IBM Options and Adapters - IBM 5.25-inch Diskette Drive Adapter
The IBM 5-1/4" Diskette Drive Adapter section of IBM's Options and Adapters technical reference is the manufacturer's own reference for the floppy controller card fitted to the IBM PC and XT.
What it contains
[edit | edit source]- Description — the NEC uPD765 or equivalent controller, double-density MFM operation with write precompensation and an analogue phase-locked loop for clock and data recovery, buffering on the I/O bus, use of the system board's DMA for record data transfer and of an interrupt level for completion and status, and support for four drives: two internal on the daisy-chained ribbon and two external through the rear-panel connector.
- Programming — the digital-output register, the main status register, the full uPD765 command summary and the programming summary.
- Drive interface — TTL signal levels, the requirement that drives provide termination networks to Vcc (except 'motor enable'), and the 150-ohm termination on each adapter input.
- Connector specifications — the 34-pin internal edge connector, with Motor Enable A on land 10, Drive Select B on 12, Drive Select A on 14 and Motor Enable B on 16, and the 37-pin external D-shell connector carrying drives C and D.
- Logic diagrams — the full schematic.
Download it here: IBM Options and Adapters - IBM 5.25-inch Diskette Drive Adapter.pdf