LP3944

SNVS264A – MAY 2004 – REVISED APRIL 2013

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Table 1. LP3944 Register Table(1)

Address (Hex)

Register Name

Read/Write

Register Function

0x00

Input 1

Read Only

LED0–7 Input Register

0x01

Register 1

Read Only

None

0x02

PSC0

R/W

Frequency Prescaler 0

0x03

PWM0

R/W

PWM Register 0

0x04

PSC1

R/W

Frequency Prescaler 1

0x05

PWM1

R/W

PWM Register 1

0x06

LS0

R/W

LED0–3 Selector

0x07

LS1

R/W

LED4–7 Selector

0x08

Register 8

R/W

None

0x09

Register 9

R/W

None

(1)

Note: Registers 1, 8 and 9 are empty and non-functional registers. Register 1 is read-only, with all bits hard-wired to zero. Registers 8

and 9 can be written and read, but the content does ot have any effect on the operation of the LP3944.

Binary Fomat for Input Registers (Read Only)—Address 0x00 and 0x01

Table 2. Address 0x00(1)

Bit #

7

6

5

4

3

2

1

0

Default value

X

X

X

X

X

X

X

X

LED7

LED6

LED5

LED4

LED3

LED2

LED1

LED0

(1)

X = don’t care

Binary Format for Frequency Prescaler and PWM Registers — Address 0x02 to 0x05

Table 3. Address 0x02 (PSC0)(1)

Bit #

7

6

5

4

3

2

1

0

Default value

0

0

0

0

0

0

0

0

(1)

PSC0 register is used to program the period of DIM0.

DIM0 = (PSC0+1)/160

The maximum period is 1.6s when PSC0 = 255.

Table 4. Address 0x03 (PWM0)(1)

Bit #

7

6

5

4

3

2

1

0

Default value

1

0

0

0

0

0

0

0

(1)

PWM0 register determines the duty cycle of DIM0. The LED outputs are LOW (LED on) when the count is less than the value in PWM0

and HIGH (LED off) when it is greater. If PWM0 is programmed with 0x00, LED output is always HIGH (LED off).

The duty cycle of DIM0 is: PWM0/256

Default value is 50% duty cycle.

Table 5. Address 0x04 (PSC1)(1)

Bit #

7

6

5

4

3

2

1

0

Default value

0

0

0

0

0

0

0

0

(1)

PSC1 register is used to program the period of DIM1.

DIM1 = (PSC1 + 1)/160

The maximum period is 1.6s when PSC1 = 255.

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