TMS279X (WD279X) FLOPPY DISK FORMATTER / CONTROLLER FAMILY

4

PIN

NUMBER

PIN NAME

SYMBOL

FUNCTION

37

DOUBLE DENSITY#

DDEN#

This input pin selects either single or double density operation.

When DDEN = 0, double density is selected. When DDEN = 1,

single density is selected.

40

HEAD LOAD TIMING

HLT

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.