UPD74HC138C

** Description **

The uPD765A/B is an LSI floppy disk controller (FDC) chip which contains the circuitry and control functions for interfacing a processor to 4 floppy disk drives. It is capableof either IBM 3740 single density format (FM), or IBM System 34 double density format (MFM) including double-sided recording. The uPD765A/B provides con trol signals which simplify the design of an external
phase-locked loop and write precompensation circuitry. The FDC simplifies and handles most of the burdens as sociated with implementing a floppy disk interface.

** Features **

Address mark detection circuitry is internal to the FDC which simplifies the phase-locked loop and read elec tronics. The track stepping rate, head load time, and head unload time are user-programmable. The uPD765A/uPD765B offers additional features such as multi-track and multi-side read and write commands and single and double density capabilities.

FM, MFM Control
Variable recording length: 128,256, .8192 bytes/ sector
IBM-compatible format (single- and double sided, single- and double-density)
Multi-sector and multi-track transfer capability
Drive up to 4 floppy or micro floppydisk drives
Data scan capability-will scan a single sector or an entire cylinder comparing byte-for-byte host memory and disk data
Data transfers in DMA or non-DMA mode
Parallel seek operations on up to four drives
Compatible with uPD8080/85, uPD8086/88, V-series and uPD780 ( [email protected] ) microprocessors
Single-phase clock: 8 MHz maximum 3 +5V only