ak4184 AKM Semiconductor, Inc., ak4184 Datasheet - Page 21

• Manufacturer Part Number: ak4184
• Description: Tsc With Keypad Scanner And Gpio Expander
• Manufacturer: AKM Semiconductor, Inc.

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The AK4184 has a keypad interface which supports a maximum Keypad matrix of six columns by five rows.
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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.
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).
MS0603-E-00
Keypad Scanner
Keypad Measurement Mode
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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.
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.
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Key press Scan Mode
Host Scan Mode
Keypad Debounce Scan initiated by Host (Initial : KST1 bit="1", KST0 bit="1")
KEYIRQN
CSN
DIN
DOUT
BUSY
State
Ry
Figure 12. Timing Diagram for keypad debounce scan initiated by Host
Enable
Detect
Key
(Initial: key interrupt enable, wait for Host instruction)
wait
KPScanInitiate
Debounce
Scan
HOLD
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Disable
Detect
Key
KPDATA1,2
Key Detect
KPScanInitiate
then wait
Enable
Debounce
Scan
data during the hold time, the
when Host reads the keypad
hold time counter will reset
after keypad data is read
KPDATA1,2
HOLD
completly.
2007/04
[AK4184]