MEC1404 Datasheet, PDF (394/572 Pages) Microchip Technology – Keyboard and Embedded Controller Products for Notebook PC

MEC140X/1X
TABLE 28-12: EC-ONLY REGISTER SUMMARY
Offset
00h
04h
08h
0Ch
10h
Register Name (Mnemonic)
LED Configuration Register
LED Limits Register
LED Delay Register
LED Update Stepsize Register
LED Update Interval Register
In the following register definitions, a “PWM period” is defined by time the PWM counter goes from 000h to its maximum
value (FFh in 8-bit mode, FEh in 7-bit mode and FCh in 6-bit mode, as defined by the PSCALE field in register
LED_CFG). The end of a PWM period occurs when the PWM counter wraps from its maximum value to 0.
The registers in this block can be written 32-bits, 16-bits or 8-bits at a time. Writes to LED Configuration Register take
effect immediately. Writes to LED Limits Register are held in a holding register and only take effect only at the end of a
PWM period. The update takes place at the end of every period, even if only one byte of the register was updated. This
means that in blink/PWM mode, software can change the duty cycle with a single 8-bit write to the MIN field in the
LED_LIMIT register. Writes to LED Delay Register, LED Update Stepsize Register and LED Update Interval Register
also go initially into a holding register. The holding registers are copied to the operating registers at the end of a PWM
period only if the Enable Update bit in the LED Configuration Register is set to 1. If LED_CFG is 0, data in the holding
registers is retained but not copied to the operating registers when the PWM period expires. To change an LED breath-
ing configuration, software should write these three registers with the desired values and then set LED_CFG to 1. This
mechanism ensures that all parameters affecting LED breathing will be updated consistently, even if the registers are
only written 8 bits at a time.
28.10.1 LED CONFIGURATION REGISTER
Offset ^00h
Bits
31:16 Reserved
16 SYMMETRY
Description
Type
R
R/W
1=The rising and falling ramp times are in Asymmetric mode.
Table 28-8, "Asymmetric Breathing Mode Register Usage" shows
the application of the Stepsize and Interval registers to the four
segments of rising duty cycles and the four segments of falling
duty cycles.
0=The rising and falling ramp times (as shown in Figure 28-2, "Breath-
ing LED Example") are in Symmetric mode. Table 28-7, "Sym-
metric Breathing Mode Register Usage" shows the application of
the Stepsize and Interval registers to the 8 segments of both ris-
ing and falling duty cycles.
15:8 WDT_RELOAD
R/W
The PWM Watchdog Timer counter reload value. On system reset, it
defaults to 14h, which corresponds to a 4 second Watchdog timeout
value.
7 RESET
W
Writes of’1’ to this bit resets the PWM registers to their default val-
ues. This bit is self clearing.
Writes of ‘0’ to this bit have no effect.
Default
-
0b
Reset
Event
-
nSYSR
ST
14h
nSYSR
ST
0b
nSYSR
ST
DS00001956D-page 394
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