PC8374L Datasheet, PDF (87/239 Pages) National Semiconductor (TI) – SensorPathTM SuperI/O with Glue Functions

Winbond Electronics Corp. Advanced PC Product Center
4.0 System Wake-Up Control (SWC) (Continued)
4.2.5 LED Control
The PC8374L device controls the operation of two LED indicators. The two open-drain buffers allow the connection of either
two regular LEDs or one dual-color LED.
The LEDs can be connected to PC8374L using one of the configurations shown in Figure 14.
V_SUP
V_SUP
V_SUP
V_SUP
R
Pin
LED
R
Pin
LED
GRN_LED
Pin
R
LED
YLW
GRN
R
YLW_LED
Pin
a. Active Low
b. Active High
Figure 14. LED Connection Configurations
c. Dual-Color
The LED pins are named GRN_LED (Green LED) and YLW_LED (Yellow LED), although other LED colors can be used.
The PC8374L allows three LED control options, which are selected by LED_OPT field in SWC_CTL register (see
Section 4.3.3 on page 92):
● _{Standard LED control: On/Off and Blink controlled by software or by S5 sleep state}
● _{Advanced LED control: On/Off and Blink controlled by software, by S3 or S5 sleep states, or by the VDD3 power sup-}
ply status
● _{Special LED control: On/Off and Blink controlled by software, by S3 or S5 sleep states or by the Main power supply}
status via the PWRGD_PS signal
From the base address of the SWC registers, the register for Standard LED Control is located at offset 00h, the two registers
for Advanced LED Control are located at offsets 02h and 03h, and the register for Special LED Control is located at offset
02h (see Section 4.3.1 on page 90). The active control registers are selected by LED_OPT field.
The blink rate and duty cycle of all LED control options are based on a clock, which is obtained by dividing the frequency of
the 32 KHz clock domain.
Standard LED Control
In this mode, two regular LEDs must be connected to the GRN_LED and the YLW_LED pins, according to configuration “b”
(Active High) in Figure 14.
In this option, LED operation is controlled by the bits of SLEDCTL register (at offset 00h; see Section 4.3.2 on page 91) and
by the SLP_S5 pin. When the system is in sleep state S5 (SLP_S5 = 0), both LEDs are off. GRN_YLW bit selects the active
LED (on or blinking) of the two; the other LED is off. BLINK bit selects the operation mode of the active LED as either con-
stantly on or blinking at 0.667 Hz with a duty cycle of 41.7% (on time percent of the blink cycle).
Table 37 on page 91 shows the states of the GRN_LED and YLW_LED pins. The LEDs are connected according to config-
uration “b” (see Figure 14); therefore, a LED is on when the pin is floated and off when the pin is at low level (0).
Advanced LED Control
In the Advanced LED control option, one dual-color LED or two regular LEDs can be connected to the GRN_LED and the
YLW_LED pins, using any of the configurations shown in Figure 14. LEDCFG and LEDPOL bits in ALEDCTL register (at
offset 02h; see Section 4.3.4 on page 93) must be set to reflect the connection configuration of the LEDs.
LEDCFG bit selects either configurations “a” and “b” (two regular LEDs are connected between each pin and ground or
V_SUPP) or configuration “c” (one dual-color LED is connected between the GRN_LED and YLW_LED pins). LEDPOL bit se-
lects the polarity of the On state at both pins (GRN_LED and YLW_LED). Table 35, shows the value of LEDCFG and LED-
POL bits for each LED connection configuration in Figure 14, and also the state of the GRN_LED and YLW_LED pins for
which the LED(s) are On.
Revision 1.1
87
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