AK4184 Datasheet, PDF (21/36 Pages) Asahi Kasei Microsystems – TSC with Keypad Scanner and GPIO Expander

[AK4184]
■ Keypad Scanner
The AK4184 has a keypad interface which supports a maximum Keypad matrix of six columns by five rows.
■ Keypad Measurement Mode
Setting the KST1 bit = “1” enables the AK4184 to monitor key-press detection and move to key pad measurement mode
after keypad detection. The AK4184 provides two different keypad measurement modes by setting the KST0 bit: host
scan mode and key press scan mode.
■ Host Scan Mode
When the KST0 bit is “1” the mode is host scan mode, pressing the keypad down makes the AK4184 outputs a
keypad interrupt signal (KEYIRQN pin goes low), and then the AK4184 move to the state which waits for a
KPScanInitiate (Page1, Address 04H) command from host. The internal oscillator turns off until receiving this
command, and the AK4184 does not execute a key scan. A keypad scan begins with receiving a
KPScanInitiate command. Once receiving this command, the AK4184 turns on the internal oscillator and starts
a keypad debounce scan.
■ Key press Scan Mode
When the KST0 bit is “0” the key press scan mode is enabled. Pressing the keypad down causes the AK4184
to output a keypad interrupt signal (KEYIRQN pin goes low) and the AK4184 starts a keypad debounce scan
automatically.
The keypad data register (KPDATA1, KPDATA2) is revised after completing a debounce scan. The KEYIQRN pin
goes to “H” and the AK4184 goes to a hold state. The key press detection function is disabled during the hold time.
When the host processor reads the keypad data register during hold time, the hold time counter is reset and restarted
after being read by the host processor. Key press detection is not valid until the host processor reads the keypad data
register after hold time is passed. Reading a keypad date is determined by accessing KPDATA1, KPDATA2 register.
Reading the KPDATA1 or KPDATA2 registers is required when the AK4184 is going to be valid for key press
interrupt. The hold time and the debounce time are controlled through the keypad control register (KEY).
Keypad Debounce Scan initiated by Host (Initial : KST1 bit="1", KST0 bit="1")
Ry
KEYIRQN
BUSY
CSN
DIN
DOUT
KPScanInitiate
KPScanInitiate
KPDATA1,2
KPDATA1,2
State
Key
Detect
Enable
wait
Debounce
Scan
HOLD
Key
Detect
Disable
Key Detect
Enable
then wait
Debounce
Scan
HOLD
when Host reads the keypad
data during the hold time, the
hold time counter will reset
after keypad data is read
completly.
Figure 12. Timing Diagram for keypad debounce scan initiated by Host
(Initial: key interrupt enable, wait for Host instruction)
MS0603-E-00
21
2007/04