LPC47M182 datasheet(45/223 Pages) SMSC

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Advanced I/O Controller with Motherboard GLUE Logic

Datasheet

SMSC LPC47M182

Revision 1.8 SMSC/Non-SMSC Register Sets (02-24-05)

DATASHEET

6.4.7

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 6.8 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 6.7 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 6.7 - Precompensation Delays

BIT 5 UNDEFINED

Should be written as a logic “0”.

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 6.10

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