TCA8418E_15 Datasheet, PDF (15/50 Pages) Texas Instruments – I2C Controlled Keypad Scan IC With Integrated ESD Protection

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8 Detailed Description
TCA8418E
SCPS222C – MAY 2010 – REVISED OCTOBER 2015
8.1 Overview
The TCA8418E supports up to 10 columns by 8 rows of keys, up to 80 keys. Any combination of these rows and
columns can be configured to be added to the keypad matrix. This is done by setting the appropriate rows and
columns to a value of 1 in the corresponding KP_GPIO registers (seen in Table 9). Once the rows and columns
that are connected to the keypad matrix are added to the keypad array, then the TCA8418E will begin monitoring
the keypad array, and any configured general purpose inputs (GPIs).
8.2 Functional Block Diagram
INT
Interrupt
Control
SCL
SDA
V_CC
I²C Bus
Control
Power-On
Reset
Control
Registers
and FIFO
Keypad
Control
ROW0–COL9
Oscillator
(32 kHz)
RESET
Figure 20. Logic Diagram (Positive Logic)
8.3 Feature Description
8.3.1 Key Events
8.3.1.1 Key Event Table
The TCA8418E can be configured to support many different configurations of keypad setups. All 18 GPIOs for
the rows and columns can be used to support up to 80 keys in a key pad array. Another option is that all 18
GPIOs be used for GPIs to read 18 buttons which are not connected in an array. Any combination in between is
also acceptable (for example, a 3 x 4 keypad matrix and using the remaining 11 GPIOs as a combination of
inputs and outputs).
For both types of inputs (keypad matrix and a GPI), a key event can be added to the key event FIFO. The values
that are added to the FIFO depend on the configuration (keypad array or GPI) and on which port the press was
read on. The tables below show the values that correspond to both types of configurations.
Key values below are represented in decimal values, because the 10s place is used to mark the row, and the
ones place is used to denote the column. It is more clear to see the numbering convention used when viewed in
decimal values.
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