MEC1322 datasheet(340/456 Pages) MICROCHIP

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MEC1322

DS00001719D-page 340

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28.10.4

LED UPDATE STEPSIZE REGISTER

This register has eight segment fields which provide the amount the current duty cycle is adjusted at the end of every

PWM period. Segment field selection is decoded based on the segment index. The segment index equation utilized

depends on the SYMMETRY bit in the LED Configuration Register Register)

• In Symmetric Mode the Segment_Index[2:0] = Duty Cycle Bits[7:5].

• In Asymmetric Mode the Segment_Index[2:0] is the bit concatenation of following: Segment_Index[2] = (FALLING

RAMP TIME in Figure 28-3, "Clipping Example") and Segment_Index[1:0] = Duty Cycle Bits[7:6].

This register may be written at any time. Values written into the register are held in an holding register, which is trans-

ferred into the actual register at the end of a PWM period if the Enable Update bit in the LED Configuration register is

set to 1. Reads of this register return the current contents and not the value of the holding register.

In 8-bit mode, each 4-bit STEPSIZE field represents 16 possible duty cycle modifications, from 1 to 16 as the duty cycle

is modified between 0 and 255:

15: Modify the duty cycle by 16

...

1: Modify the duty cycle by 2

0: Modify the duty cycle by 1

In 7-bit mode, the least significant bit of the 4-bit field is ignored, so each field represents 8 possible duty cycle modifi-

cations, from 1 to 8, as the duty cycle is modified between 0 and 127:

14, 15: Modify the duty cycle by 8

...

2, 3: Modify the duty cycle by 2

0, 1: Modify the duty cycle by 1

In 6-bit mode, the two least significant bits of the 4-bit field is ignored, so each field represents 4 possible duty cycle

modifications, from 1 to 4 as the duty cycle is modified between 0 and 63:

12, 13, 14, 15: Modify the duty cycle by 4

8, 9, 10, 11: Modify the duty cycle by 3

4, 5, 6, 7: Modify the duty cycle by 2

0, 1, 2, 3: Modify the duty cycle by 1

Offset

0Ch

Bits

Description

Type

Default

Reset

Event

31:28 UPDATE_STEP7