NEC uPD765 Data Sheet Dec78 free download

File name uPD765_Data_Sheet_Dec78.pdf

NEe NEe Microcomputers, Inc. fLPD765 SINGLE/DOUBLE DENSITY FLOPPY DISK CONTROLLER' OESCRI PTION The J.1PD765 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 capable of supporting either IBM 3740 single density format (FM), or IBM System 34 Double Density format (MFM) including double sided recording. The J.1PD765 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 J.1PD765 which make DMA operation easy to incorporate with the aid of an external DMA Controller chip, such as the J.1PD8257. The FDC will operate in either DMA or Non-DMA mode. In the Non-DMA mode, the FDC generates interrupts to the processor every time a data byte is available. In the DMA mode, the processor need only load the command into the FDC and all data transfers occur under control of the J.1PD765 and DMA controller. There are 15 separate commands which the J.1PD765 will execute. Each of these commands requ ire multiple 8-bit bytes to fully specify the operation which the processor wishes the F DC to perform. The following commands are available: Read Data Scan High or Equal Write Deleted Data Read ID Scan Low or Equal Seek Read Deleted Data Specify Recalibrate (Restore to Track 0) Read a Track Write Data Sense I nterrupt Status Scan Equal Format a Track Sense Drive Status