UPD765B Datasheet, PDF (1/17 Pages) NEC – Single/Double Density Floppy-Disk Controller

NEC
NEC Electronics Inc.
uPD765A/uPD765B
Single/Double Density
Floppy-Disk Controller
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 3740singledensity 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.
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 the
uPD8257. 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.
Read Data
Read ID
Specify
Read Diagnostic
Scan Equal
Scan High or Equal
Scan Low or Equal
Version
Read Deleted Data
Write Data
Write ID (Format Write)
Write Deleted Data
Seek
Recalibrate
Sense Interrupt Status
Sense Drive Status.
Ordering Information
Device Number
uPD765AC2
uPD765B
Package Type
40-pin plastic DIP
40-pin plastic DIP
Max Freq. of Operation
8 MHz
8 MHz
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,
and uPD780 (Z80@) microprocessors
V-series
Single-phase clock: 8 MHz maximum
3 +5V only
Z80 is a registered trademark of the Zilog Corporation
Pin Configuration
NECEL-000324
5-3