TMS279X datasheet(10/40 Pages) TI

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TMS279X (WD279X) FLOPPY DISK FORMATTER / CONTROLLER FAMILY

TABLE 2 - FLAG SUMMARY

COMMAND

TYPE

BIT

NUMBER(S)

DESCRIPTION

0, 1

r1 r0 = Stepping Motor Rate

See Table 3 for Rate Summary

V = Track Number Verify Flag

V = 0, No verify

V = 1, Verify on destination track

h = Head Load Flag

h = 0, Unload head at beginning

h = 1, Load head at beginning

T = Track Update Flag

T = 0, No update

T = 1, Update track register

II & III

a0 = Data Address Mark

a0 = 0, FB (DAM)

a0 = 1, F8 (deleted DAM)

C = Side Compare Flag

C = 0, Disable side compare

C = 1, Enable side compare

II & III

U = Update SSO

U = 0, Update SSO to 0

U = 1, Update SSO to 1

II & III

E = 1 5 ms Delay

E = 0, No. 15 ms delay

E = 1, 15 ms delay (30 ms for 1 MHz)

S = Side Compare Flag

S = 0, Compare for side 0

S = 1, Compare for side 1

L = Sector Length Flag

LBS's Sector Length in ID Field

L=0

256

512

1024

128

L=1

128

256

512

1024

m = Multiple Record Flag

m=0, Single record

m=1, Multiple record

0-3

Ix = Interrupt Condition Flags

I0 = 1 Not Ready to Ready Transition

I1 = 1 Ready To Not Ready Transition

I2 = 1 Index Pulse

I3 = 1 Immediate Interrupt, Requires A Reset*

I3-I0 = 0 Terminate With No Interrupt (INTRQ)

*See Type IV command for further information.

write precompensation

When operating in double density mode (DDEN = 0), the 279X has the capability of providing a user-defined

precompensation value for write data. An external potentiometer (10 k?) tied to the WPW signal (pin 33)

allows a setting of 100 to 300 ns from nominal.

Setting the write precomp value is accomplished by forcing the TEST# line (pin 22) to a logic 0. A stream of

pulses can then be seen on the write data (pin 31) line. Adjust the WPW potentiometer for the desired pulse

duration. This adjustment may be performed in-circuit since write gate (pin 30) is inactive while TEST# = 0.

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