Communication ICs
Panel interface for telephones
The BU8317KV is a large-scale integrated circuit which enables a serial input / output interface between the key input
required for panel boards used in PHS systems, portable telephones, and telephone answering machines and LED and
LCD control functions. It reduces the number of wiring harnesses needed between the main board in the telephone and
the panel board, and takes some of the processing load off the main CPU.
PHS systems, portable telephones, telephone answering machines
1) 7 7 keypad matrix interface.
2) 12-bit LED driver. (6 bits can also function as input
3) 4-column 32-segment LCD driver. (internal bias-generating resistor)
4) Standby mode.
5) VQFP80 package.
Absolute maximum ratings (unless otherwise noted, Ta = 25C)
Recommended operating conditions (Ta = 25C)
Communication ICs
Block diagram
Pin descriptions
Communication ICs
Communication ICs
Input / output circuits
Communication ICs
Electrical characteristics (unless otherwise noted, Ta = 25C, VDD=2.7 to 5.5V)
Communication ICs
Timing charts
Communication ICs
Measurement circuits
Communication ICs
Data formats (Serial data is input and output with the MSB coming first.)
(1) Reading data
R1XR7, C1XC7
LED resitor writing command
Used for LED control. LED lights up with “1” and is unlit with “0”.
LCD register writing command
: Outputs SR pin status. Pressing a key (low level) outputs “1” and
releasing the key (high level) outputs “0”.
A “0” is output is the key is not pressed on low level.
: Outputs key data. Pressing a key outputs “1” and not pressing the
key outputs “0”, when on low level.
: Outputs parallel input data. Output “1” when the pin is on high level and “0” when it is on low level.
: Selects LCD common. “1” means select and “0” means do not select.
Segment control is active on the selected common, only.
Multiple commons can be selected simultaneously.
: Used for LCD segment control. Lights up with “1” and is unlit with
Communication ICs
All LEDs, LCDs activate command
Used to clear non-active status of all LEDs and LCDs.
All LEDs, LCDs non-active command
Temporarily turns off all LEDs and LCDs, while holding the LED and LCD register settings as they are.
LCD output changes to low level and the bias current channel is cut.
(6) Register reset command
Resets all LED and LCD resisters to “0”.
Clears stand-by mode.
Non-active status of all LEDs and LCDs changes to active status.
Communication ICs
Recommended method for inputting / outputting data
(1) Control command serial input
Key data serial output
Communication ICs
FStandby mode
(1) Setting the standby mode
S The standby mode is set by setting RE to L and WE to L.
S Oscillation stops and the line current falls to an extremely low level.
S The contents of the LED and LCD registers are reset (all data cleared to 0), and all LEDs and LCDs are
turned off.
S The LCD output goes LOW, and the bias current channel is cut off.
S The only effective key input is the SR key; no input is accepted from the keypad.
Cancelling the standby mode
S The standby mode is cancelled by executing the register reset command.
S Setting SR to LOW in any state other than RE = LOW and WE = LOW immediately cancels the standby
S Setting SR to LOW when RE = LOW and WE = LOW initiates oscillation but does not cancel the standby
mode. Setting SR to HIGH stops oscillation once again.(If “on debounce” is valid for the SR key and KD
has output a LOW level, oscillation continues until an “off debounce” becomes valid.)
Standby mode setting example
At RE = LOW, WE = LOW, the standby mode is set, and oscillation stops.
In standby mode, no input is accepted.
Setting the SR pin to LOW initiates oscillation even in the standby mode.
(SR = LOW takes priority over RE = LOW, WE = LOW.)
When the SR pin is open (HIGH), RE = LOW and WE = LOW, so oscillation stops and the standby mode continues
to be effective.
Setting the SR pin LOW initiates oscillation even in the standby mode.
When RE = LOW, WE = LOW is no longer true, the standby mode is cancelled, and oscillation continues even if the
SR pin is open (HIGH).
Data is set in the output serial register at the falling edge of RE and when SR = LOW, and can be read.
Communication ICs
Oscillation frequencies
LCD drive wave forms
This is a time-shared drive system in
which 1 / 3 bias and 1 / 4 duty alternate
between two frames.
The figure at the right shows the drive
wave forms for the following conditions :
LC01-LSxx : Lighted
LC02-LSxx : Not lighted
LC03-LSxx : Lighted
LC04-LSxx : Not lighted
Communication ICs
Configuring a booster circuit
This shows an example of booster circuit configuration for a VLCD pin, using the CPC and CPCB pins.
Configuring an LCD bias correction circuit
This shows an example of correction circuit configuration for the LCD output voltage, using the V3 pin.
Communication ICs
Precautions when turning on the power supply
The power supply should be turned on when RE = LOW and WE = LOW, and the registers should then be reset using
the register reset command.
Precautions concerning data input and output
(1) Serial output of key data when several keys are
pressed at the same time is as shown at the right.
The key data when 1. and (1) are pressed at the
same time is the same as the key data when 2. and
3. are pressed at the same time.
If the LED and LCD registers are rewritten, all of the bits should be written, and not just the pertinent bits.
Electrical characteristic curve
External dimensions (Units: mm)