ADP5586ACBZ-00-R7 datasheet(9/44 Pages) AD

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Data Sheet

ADP5586

Rev. 0 | Page 9 of 44

FUNCTIONAL DESCRIPTION

EVENT FIFO

Before going into detail on the various blocks of the ADP5586,

it is important to understand the function of the event FIFO that

is featured in the ADP5586. The event FIFO (Register 0x03 to

FIFO primarily records key events, such as key press and key

release. However, it is possible to configure the general-purpose

input (GPI) and logic activity to generate event information

on the FIFO, as well. An event count, EC[4:0] (Register 0x02,

Bits[4:0]), is composed of five bits and works in tandem with

the FIFO so that the user knows how many events are stored

in the FIFO.

The FIFO consists of sixteen 8-bit elements. Bits[6:0] of each

element store the event identifier, and Bit 7 stores the event

state. The user can read the top element of the FIFO from any

of the FIFO_1 through FIFO_16 registers. The ADP5586 has

multiple copies of the FIFO register to allow reading of the

complete FIFO with a single I2C burst read.

EVENT1[7:0]

EVENT2[7:0]

EVENT3[7:0]

EVENT4[7:0]

EVENT13[7:0]

EVENT14[7:0]

EVENT15[7:0]

EVENT16[7:0]

EVENT5[7:0]

EVENT6[7:0]

EVENT7[7:0]

EVENT8[7:0]

EVENT9[7:0]

EVENT10[7:0]

EVENT11[7:0]

EVENT12[7:0]

GPI EVENTS

EC[4:0]

OVRFLOW_INT

KEY EVENTS

LOGIC EVENTS

FIFO

UPDATE

EVENT8_IDENTIFIER[6:0]

EVENT8_STATE

Figure 6. Breakdown of Eventx[7:0] Bits

KEY 3 PRESSED

KEY 3 RELEASED

GPI 7 ACTIVE

EC = 3

KEY 3 RELEASED

GPI 7 ACTIVE

EC = 2

GPI 7 ACTIVE

EC = 1

EC = 0

THIRD

READ

SECOND

READ

FIRST

READ

Figure 7. FIFO Operation

The FIFO registers always point to the top of the FIFO (that is, the

location of EVENT1[7:0]). If the user tries to read back from any

location in a FIFO, data is always obtained from the top of that

FIFO. This ensures that events can be read back only in the order

in which they occurred, thereby ensuring the integrity of the

FIFO system.

As stated previously, some of the on-board functions of the

ADP5586 can be programmed to generate events on the FIFO.

A FIFO update control block manages updates to the FIFO.

If an I2C transaction is accessing any of the FIFO address

locations, updates are paused until the I2C transaction is complete.

A FIFO overflow event occurs when more than 16 events are

generated prior to an external processor reading a FIFO and

clearing it.

If an overflow condition occurs, the overflow interrupt status

bit is set (OVRFLOW_INT, Register 0x01, Bit 2). An interrupt

is generated if an overflow interrupt is enabled, signaling to the

processor that more than 16 events have occurred.

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