ZHCS290G September 2009 – June 2018 TCA8418
PRODUCTION DATA.
| ADDRESS | REGISTER NAME(1) | REGISTER DESCRIPTION | BIT | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |||
| 0x04 | KEY_EVENT_A | Key event register A | KEA7 | KEA6 | KEA5 | KEA4 | KEA3 | KEA2 | KEA1 | KEA0 |
These registers – KEY_EVENT_A-J – function as a FIFO stack which can store up to 10 key presses and releases. The user first checks the INT_STAT register to see if there are any interrupts. If so, then the Key Lock and Event Counter Register (KEY_LCK_EC, register 0x03) is read to see how many interrupts are stored. The INT_STAT register is then read again to ensure no new events have come in. The KEY_EVENT_A register is then read as many times as there are interrupts. Each time a read happens, the count in the KEY_LCK_EC register reduces by 1. The data in the FIFO also moves down the stack by 1 too (from KEY_EVENT_J to KEY_EVENT_A). Once all events have been read, the key event count is at 0 and then KE_INT bit can be cleared by writing a ‘1’ to it.
In the KEY_EVENT_A register, KEA[6:0] indicates the key # pressed or released. A value of 0 to 80 indicate which key has been pressed or released in a keypad matrix. Values of 97 to 114 are for GPI events.
Bit 7 or KEA[7] indicate if a key press or key release has happened. A ‘0’ means a key release happened. A ‘1’ means a key has been pressed (which can be cleared on a read).
For example, 3 key presses and 3 key releases are stored as 6 words in the FIFO. As each word is read, the user knows if it is a key press or key release that occurred. Key presses such as CTRL+ALT+DEL are stored as 3 simultaneous key presses. Key presses and releases generate key event interrupts. The KE_INT bit and /INT pin will not cleared until the FIFO is cleared of all events.
All registers can be read but for the purpose of the FIFO, the user should only read KEY_EVENT_A register. Once all the events in the FIFO have been read, reading of KEY_EVENT_A register will yield a zero value.