LPC47M192 datasheet(36/228 Pages) SMSC

36 / 228 page

SMSC DS – LPC47M192

Page 36

Rev. 03/30/05

DATASHEET

DATA RATE SELECT REGISTER (DSR)

Address 3F4 WRITE ONLY

This register is write only. It is used to program the data rate, amount of write precompensation, power down status,

and software reset. The data rate is programmed using the Configuration Control Register (CCR) not the DSR, for

PC/AT and PS/2 Model 30.

S/W

RESET

POWER

DOWN

PRE-

COMP2

PRE-

COMP1

PRE-

COMP0

DRATE

SEL1

DRATE

SEL0

RESET

COND.

This register is write only. It is used to program the data rate, amount of write precompensation, power down status,

and software reset. The data rate is programmed using the Configuration Control Register (CCR) not the DSR, for

PC/AT and PS/2 Model 30.

Other applications can set the data rate in the DSR. The data rate of the floppy controller is the most recent write of

either the DSR or CCR. The DSR is unaffected by a software reset. A hardware reset will set the DSR to 02H, which

corresponds to the default precompensation setting and 250 Kbps.

BIT 0 and 1 DATA RATE SELECT

These bits control the data rate of the floppy controller. See Table 8 for the settings corresponding to the individual

data rates. The data rate select bits are unaffected by a software reset, and are set to 250 Kbps after a hardware

reset.

BIT 2 through 4 PRECOMPENSATION SELECT

These three bits select the value of write precompensation that will be applied to the WDATA output signal. Table 7

shows the precompensation values for the combination of these bits settings. Track 0 is the default starting track

number to start precompensation. This starting track number can be changed by the configure command.

Table 7 – Precompensation Delays

BIT 5 UNDEFINED

Should be written as a logic “0”.

BIT 6 LOW POWER

A logic “1” written to this bit will put the floppy controller into manual low power mode. The floppy controller clock and

data separator circuits will be turned off. The controller will come out of manual low power mode after a software

reset or access to the Data Register or Main Status Register.

BIT 7 SOFTWARE RESET

This active high bit has the same function as the DOR RESET (DOR bit 2) except that this bit is self clearing.

PRECOMP

432

PRECOMPENSATION

DELAY (nsec)

<2Mbps

2Mbps

111

001

010

011

100

101

110

000

0.00

41.67

83.34

125.00

166.67

208.33

250.00

Default

20.8

41.7

62.5

83.3

104.2

125

Default

Default: See Table 10

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