SCPS215G September   2009  – June 2018 TCA8418

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information
    5. 6.5  Electrical Characteristics
    6. 6.6  I2C Interface Timing Requirements
    7. 6.7  Reset Timing Requirements
    8. 6.8  Switching Characteristics
    9. 6.9  Keypad Switching Characteristics
    10. 6.10 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Key Events
        1. 8.3.1.1 Key Event Table
        2. 8.3.1.2 General Purpose Input (GPI) Events
        3. 8.3.1.3 Key Event (FIFO) Reading
        4. 8.3.1.4 Key Event Overflow
      2. 8.3.2 Keypad Lock/Unlock
      3. 8.3.3 Keypad Lock Interrupt Mask Timer
      4. 8.3.4 Control-Alt-Delete Support
      5. 8.3.5 Interrupt Output
        1. 8.3.5.1 50 Micro-second Interrupt Configuration
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-On Reset (POR)
      2. 8.4.2 Powered (Key Scan Mode)
        1. 8.4.2.1 Idle Key Scan Mode
        2. 8.4.2.2 Active Key Scan Mode
    5. 8.5 Programming
      1. 8.5.1 I2C Interface
      2. 8.5.2 Bus Transactions
        1. 8.5.2.1 Writes
        2. 8.5.2.2 Reads
    6. 8.6 Register Maps
      1. 8.6.1 Device Address
      2. 8.6.2 Control Register and Command Byte
        1. 8.6.2.1  Configuration Register (Address 0x01)
        2. 8.6.2.2  Interrupt Status Register, INT_STAT (Address 0x02)
        3. 8.6.2.3  Key Lock and Event Counter Register, KEY_LCK_EC (Address 0x03)
        4. 8.6.2.4  Key Event Registers (FIFO), KEY_EVENT_A–J (Address 0x04–0x0D)
        5. 8.6.2.5  Keypad Lock1 to Lock2 Timer Register, KP_LCK_TIMER (Address 0x0E)
        6. 8.6.2.6  Unlock1 and Unlock2 Registers, UNLOCK1/2 (Address 0x0F-0x10)
        7. 8.6.2.7  GPIO Interrupt Status Registers, GPIO_INT_STAT1–3 (Address 0x11–0x13)
        8. 8.6.2.8  GPIO Data Status Registers, GPIO_DAT_STAT1–3 (Address 0x14–0x16)
        9. 8.6.2.9  GPIO Data Out Registers, GPIO_DAT_OUT1–3 (Address 0x17–0x19)
        10. 8.6.2.10 GPIO Interrupt Enable Registers, GPIO_INT_EN1–3 (Address 0x1A–0x1C)
        11. 8.6.2.11 Keypad or GPIO Selection Registers, KP_GPIO1–3 (Address 0x1D–0x1F)
        12. 8.6.2.12 GPI Event Mode Registers, GPI_EM1–3 (Address 0x20–0x22)
        13. 8.6.2.13 GPIO Data Direction Registers, GPIO_DIR1–3 (Address 0x23–0x25)
        14. 8.6.2.14 GPIO Edge/Level Detect Registers, GPIO_INT_LVL1–3 (Address 0x26–0x28)
        15. 8.6.2.15 Debounce Disable Registers, DEBOUNCE_DIS1–3 (Address 0x29–0x2B)
        16. 8.6.2.16 GPIO pull-up Disable Register, GPIO_PULL1–3 (Address 0x2C–0x2E)
      3. 8.6.3 CAD Interrupt Errata
        1. 8.6.3.1 Description
        2. 8.6.3.2 System Impact
        3. 8.6.3.3 System Workaround
      4. 8.6.4 Overflow Errata
        1. 8.6.4.1 Description
        2. 8.6.4.2 System Impact
        3. 8.6.4.3 System Workaround
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Ghosting Considerations
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Designing the Hardware Layout
        2. 9.2.2.2 Configuring the Registers
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.3.1.4 Key Event Overflow

The TCA8418 has the ability to handle an overflow of the key event FIFO. An overflow event occurs when the FIFO is full of events (10 key events are stored) and a new key event occurs. In short, this means that the TCA8418 does not have the ability to hold any more key press information in the internal buffer. When this occurs, the OVR_FLOW_INT bit in the INT_STAT Register is set, and if the OVR_FLOW_IEN bit is set in the CFG Register, then the INT output will be asserted low to let the processor know that an overflow has occurred.

The TCA8418 has the ability to handle an overflow in 1 of two ways, which is determined by the bit value of the OVR_FLOW_M bit in the CFG Register.

Please see the Overflow Errata section for more information about overflow behavior.

Table 6. OVR_FLOW_M Bit

OVR_FLOW_M Value Overflow Mode Behavior
1 Enabled Overflow data shifts with last event pushing first event out
0 Disabled (Default) Overflow data is not stored and lost

Consider the example below, if the FIFO is full of the key presses and a new key press comes in. This new overflow key press will be a key press of key 2 (0x82 is the hex representation of a key 2 press event)

Table 7. Key Event Overflow Handling

FIFO Register Original Value After Key 1 Press Event (0x82)
OVR_FLOW_M = 1 OVR_FLOW_M = 0
A 0x81 0xA0 0x81
B 0xA0 0x01 0xA0
C 0x01 0x20 0x01
D 0x20 0x97 0x20
E 0x97 0x17 0x97
F 0x17 0xAD 0x17
H 0xAD 0xA9 0xAD
I 0xA9 0x29 0xA9
J 0x29 0x2D 0x29
K 0x2D 0x82 0x2D