LM8327 datasheet(12/65 Pages) TI2

12 / 65 page

LM8327

SNLS329A – SEPTEMBER 2011 – REVISED MAY 2013

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Since the interrupt pin has various sources, the host first checks the IRQST register for the interrupt source. If

KBDIRQ is set, the host can check the KBDMIS register to define the exact interrupt source. KBDMIS contains

the masked status of KBDRIS and reflects the source for raising the interrupt pin. The interrupt mask is defined

by KBDMSK. The complete status of all pending keyboard interrupts is available in the raw interrupt register

KBDRIS.

After evaluating the interrupt source the host starts reading the EVTCODE or KBDCODE register. In this

example the host first reads the KBDCODE to get possible key press events and afterwards reads the complete

event list by reading the EVTCODE register until all events are captured (0x7F indicates end of buffer).

Reading KBDCODE clears the RSINT interrupt bit if all keyboards events are emptied. In the same way,

REVTINT is cleared in case the EVTCODE FIFO reaches its empty state on read.

The event buffer content and the REVTINT and RELINT (lost event) interrupt bits are also cleared if the

KBDIC.EVTIC bit is set.

Interrupt bits in the masked interrupt register KBDMIS follow the masked KBDRIS status.

In order to support efficient Multi-byte reads from EVTCODE, the autoincrement feature is turned off for this

Figure 8. Example Host Reacting to

Interrupt for Keypad Event

MULTIPLE KEY PRESSES

The LM8327 supports up to four simultaneous key presses. Any time a single key is pressed KBDCODE0 is set

with the appropriate key code. If a second key is pressed, the key is stored in KBDCODE1 and the MULTIKEY

flag of KBDCODE0 is set. Additional key presses are stored in KBDCODE2 and KBDCODE3 accordingly. The

four registers signal the last multi-key press events.

All events are stored in parallel in the EVTCODE register for the complete set of events.

All KBDCODE[3:0] registers are cleared on read.

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LM8327 Datasheet(PDF) 12 Page - Texas Instruments