TMS279X Datasheet, PDF (4/40 Pages) Texas Instruments – FLOPPY DISK FORMATTERICONTROLLER FAMILY

TMS279X (WD279X) FLOPPY DISK FORMATTER / CONTROLLER FAMILY
PIN
NUMBER
PIN NAME
37 DOUBLE DENSITY#
40 HEAD LOAD TIMING
SYMBOL
FUNCTION
DDEN#
HLT
This input pin selects either single or double density operation.
When DDEN = 0, double density is selected. When DDEN = 1,
single density is selected.
When a logic high is found on the HLT input the head is
assumed to be engaged. It is typically derived from a 1 shot
triggered by HLD.
system interface
The TMS279X Floppy Disk Formatter/Controller system interface is shown in Figure 1. This interface
consists of the parallel processor interface and the floppy disk interface. Applications for the TMS279X family
are 8" floppy and 5 1/4" mini-floppy controller and single- or double-density controller/formatter.
The TMS279X family are MOS/LSI devices which perform the functions of a Floppy Disk Controller /
Formatter. Software compatible with its predecessor, the FD179X the device also contains a high
performance phase-lock-loop data separator as well as write precompensation logic.
When operating in double-density mode, write precompensation may be enabled, its value predetermined by
an external potentiometer. An on-chip VCO and phase comparator allows adjustable frequency range for
5 1/4" or 8" floppy disk interfacing.
The TMS279X is fabricated in NMOS silicon gate technology and available in a 40-pin dual-in-line package.
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