•

On-Chip PILL Data Separator

•

On-Chip Write Precompensation Logic

•

Single + 5-V Supply

•

Accommodates Single-and Double-Density Formats

- MM3740 (FM)

- IBM34 (MFM)

•

Automatic Seek with Verify

•

Multiple Sector Read/Write

•

TTL Compatible

•

Programmable Control

- Selectable Track-to-Track Access

- Head Load Timing

•

Software Compatible with the FD179X Series

•

Soft Sector Format Compatibility

description

The TMS279X family are N-channel silicon

gate MOS LSl devices which perform the

functions of a Floppy Disk Formatter/Controller

in a single chip implementation. The TMS279X,

which can be considered the end result of both

the Western Digital FD1771 and FD179X

designs, is IBM compatible in single-density

mode (FM) and System 34 compatible in

double-density mode (MFM). The TMS279X

contains all the features of its predecessor the FD179X plus a high performance phase-lock-loop data

separator as well as write precompensation logic. In double-density mode, write precompensation is

automatically engaged to a value programmed via an external potentiometer. In order to maintain

compatibility, the FD1771, FD179X and TMS279X designs were made as close as possible with the

computer interface, instruction set, and I/O registers being identical. Also, head load control is identical. In

each case, the actual pin assignments vary by only a few pins from any one to another.

The processor interface consists of an 8-bit bi-directional bus for data, status, and control word transfers.

The TMS279X is set up to operate on a multiplexed bus with other bus-oriented devices.

The TMS279X is TTL compatible on all inputs and outputs. The outputs will drive one TTL load or three LS

loads. The 2793 is identical to the 2791 except the DAL lines are true for systems that utilize true data

busses.

The 2795/7 has a side-select output for controlling double-sided drives.

PROGRAMMABLE

TMS279X

PRODUCTS

FLOPPY DISK FORMATTERICONTROLLER FAMILY

JUNE 1984

FEATURES

2791

2793

2795

2797

Single Density (FM)

X

X

X

X

Double Density (MFM)

X

X

X

X

True Data Bus

X

X

Inverted Data Bus

X

X

Side Select Out

X

X

Internal CLK Divide

X

X

Scanned and Edited by Michael Holley - Aug 21, 2001 - HolleyMJ@aol.com

Texas Instruments was a second source for the WD279X and this data sheet is almost identical to the

Western Digital WD279X-02 Data Sheet and Application Note. (But has larger figures and is more readable.)

Active low signals use a trailing # instead of an overbar.