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UPD765BC / nec ic / 100 pieces
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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 3740singledensity format (FM), or IBM System 34 double density format (MFM) including double-sided recording. The uPD765A/B provides control signals which simplify the design of an external phase-locked loop and write precompensation circuitry.
The FDC simplifies and handles most of the burdens associated with implementing a floppy disk interface.
Hand-shaking signals are provided in the uPD765A/B which make DMA operation easy to incorporate with the aid of an external DMA controller chip, such as theuPD8257. The FDC will operate in eitherthe DMA or non- DMA mode. In the non-DMA mode the FDC generates interrupts to !he processor every time a data byte is to be transferred. In the DMA mode, the processor need only load the command into the FDC and all data transfers occur under control of the FDC and DMA controllers.
There are 16 commands which the uPD765A/uPD765B will execute. Most of these commands require multiple 8-bit bytes to fully specify the operation which the processor wishes the FDC to perform. The following commands are available.
Specify Write ID (Format Write)
Read Diagnostic Write Deleted Data
Scan High or Equal Recalibrate
Scan Low or Equal Sense Interrupt Status
Address mark detection circuitry is internal to the FDC which simplifies the phase-locked loop and read electronics.
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.
* Variable recording length: 128,256, .8192 bytes/sector
* IBM-compatible format (single- and doublesided, 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 (Z80@) microprocessors
* Single-phase clock: 8 MHz maximum
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