AK4184 Datasheet, PDF (12/36 Pages) Asahi Kasei Microsystems – TSC with Keypad Scanner and GPIO Expander

[AK4184]
■ Keypad Scanner
The AK4184 keypad scanner is designed to interface to a matrix type keypad with 5 rows x 6 columns (30keys or
fewer) to the host controller. The KPMASK1, 2 and KPColumnMask register enable the masking of certain keys or a
whole column of the keypad when any keys less than 30 keys or any columns less than 6 columns are not utilized.
■ Keypad Interrupt Detection
When the AK4184 is in key interrupt enabled mode, C1~C6 pins are designed to output “H” and R1~R5 pins are
designed to pull to GND via Rkey (Rkey=16kΩ typ, Figure 5). When a key is pressed a related R1~R5 pin goes “H”
and the KEYIRQN pin goes “L”. The KEYIRQN pin returns “H” after key press scan is completed. KEYIRQN pin
does not go “L” again until the host reads the keypad read register (KPDATA1 or KPDATA2).
■ Keypad Scan Data Read
The AK4184 starts to scan the key condition in sequence and writes each keypad state to the registers after a key-
press is detected. First the C1 pin goes to “H” (Scan Output1) and the C2 ~ C6 pins are in Hi-Z state. Certain Ry pins
are connected to C1 and pulled “H”. The Ry pin returns “L” after the key-press is released. The AK4184 reads the Ry
pin level (Sense Input 1 through 5) and loads the keypad data into the register. When two keys are pressed
simultaneously, the associated row pins go “H” at the same time. Then the AK4184 C2 pin goes to “H” (Scan
Output2), and reads and loads the R1 ~ R5 pin levels into the register (Sense Input 1 through 5). The same sequence
as Scan Output 1 repeats up to Scan Output 6. The AK4184 makes this Scan Output and Sense Input pattern and loads
the keypad-data into the register for unmasked columns.
Debounce key scan performs a series of the Scan Output / Sense Input at the end of the debounce time interval, then
the AK4184 loads the key pad data into the resister. μ-Processor starts to read the data register after confirming if the
keypad scan completed. New keypad scan does not repeat again until the Host reads the keypad data.
MS0603-E-00
12
2007/04