MEC1404 Datasheet, PDF (397/572 Pages) Microchip Technology – Keyboard and Embedded Controller Products for Notebook PC

MEC140X/1X
• 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
31:28 UPDATE_STEP7
Amount the current duty cycle is adjusted at the end of every PWM
period when the segment index is equal to 111.
27:24 UPDATE_STEP6
Amount the current duty cycle is adjusted at the end of every PWM
period when the segment index is equal to 110.
23:20 UPDATE_STEP5
Amount the current duty cycle is adjusted at the end of every PWM
period when the segment index is equal to 101
19:16 UPDATE_STEP4
Amount the current duty cycle is adjusted at the end of every PWM
period when the segment index is equal to 100.
15:12 UPDATE_STEP3
Amount the current duty cycle is adjusted at the end of every PWM
period when the segment index is equal to 011.
11:8 UPDATE_STEP2
Amount the current duty cycle is adjusted at the end of every PWM
period when the segment index is equal to 010.
Type
R/W
R/W
R/W
R/W
R/W
R/W
Default
0h
Reset
Event
nSYSR
ST
0h
nSYSR
ST
0h
nSYSR
ST
0h
nSYSR
ST
0h
nSYSR
ST
0h
nSYSR
ST
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DS00001956D-page 397