STFPC320 STMicroelectronics, STFPC320 Datasheet - Page 15

• Manufacturer Part Number: STFPC320
• Description: Front Panel Controller/driver With Standby Power Management And Real-time Clock
• Manufacturer: STMicroelectronics

STFPC320
4.7
4.8
4.9
4.10
4.10.1
4.10.2
Mute pin
The MUTE pin will be set to logic high to mute the audio output before power is cut to the
host processor. In wake up mode, the MUTE pin will be set to logic low to enable the audio
output immediately after the high assertion of the READY pin. In general, MUTE follows
READY pin with an inverted polarity. This pin is used to prevent pop-up sound during power-
up and power-down states.
Key-Scan matrix / front panel keys
The key scan matrix on the STFPC320 helps to pass command from the front panel to the
host processor through the SDA pin on STFPC320. The STFPC320 can be programmed to
wake-up the system from standby using any of the 24 keys pressed on the front panel.
These wake-up keys are also referred to as hot-keys.
LED ports
4 LED displays are supported by the STFPC320. Turning on or off of the LED is done by
issuing write command to the LED port. After reset, the LEDs are off. Note that the LED
outputs sink the current, so the cathode of the diode must be connected to the LED pins of
STFPC320.
Display
The display is divided into two sections, Normal and Real Time Clock (RTC).
Normal display
The VFD display is configurable for displays from 8 digits/20 segments to 16 digits/12
segments. The VFD display can be configured to be either in the normal VFD mode or in the
RTC mode. In the normal VFD mode, the display shows whatever is written in the VFD
display memory.
If the user desires to show normal display simultaneously with the RTC, then CPU must
read the time of RTC display memory and then write all the data to be displayed to the
normal display memory. After writing the values to the display memory, a display-on
command will show both the normal and RTC display on the front panel.
On first power on, the default configuration is 16-digit, 12-segment mode (with display
turned OFF).
RTC display
In RTC mode, the display can be configured to show the time in two modes, either by direct
mapping of RTC to the display or by using the CPU. If CPU is used, the CPU reads the RTC
value from RTC registers and then writes the time to be displayed in the RTC display
memory.
Functional description
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