8.0 Interrupts

8.1 INTERRUPT CODE

The interrupt code is read and acknowledged with the

READ_INT command (0xD0). This command clears the

code and deasserts the IRQ output. Table 6 shows the

format of the interrupt code.

Note that when only one of the interrupt-capable pins GE-

N_IO_0 or GEN_IO_1 is configured as an interrupt input, bits

1 and 2 are both set when an interrupt occurs. When both

GEN_IO_0 and GEN_IO_1 pins are configured as interrupt

inputs, only one bit corresponding to the interrupt source is

set when an interrupt occurs.

TABLE 6. Interrupt Code

76

5

4

3

2

1

0

0

0

0

0

ERROR

EX_1

EX_0

KEYPAD

Bit

Description

ERROR

An error condition occurred.

EX_1

A rising or falling edge was detected on GEN_IO_1.

EX_0

A rising or falling edge was detected on GEN_IO_0.

KEYPAD

A key-press or key-release event occurred.

8.2 ERROR CODE

If the LM8333 reports an error, the READ_ERROR com-

mand (0xF0) is used to read and clear the error code. Table

7 shows the format of the error code.

TABLE 7. Error Code

76

5

4

3210

0

FIFOOVR

0

NOINT

0

KEYOVR

CMDUNK

CMDOVR

Bit

Description

FIFOOVR

Key event occurred while the FIFO was full.

NOINT

Interrupt deasserted before it could be serviced.

KEYOVR

More than two keys were pressed simultaneously.

CMDUNK

Not a valid command.

CMDOVR

Command received before it could be accepted, e.g. after wake-up.

8.3 STATUS CODES

The host can use the READ_STAT command (0xE0) to read

the status code, for example to synchronize after an error.

TABLE 8. Status Codes

Status

Code

Description

Reset

0000 0000

Default after reset.

Wake Up Interrupt

0000 0010

Wake-up caused by external interrupt.

Ack

0000 0110

Last host command was successful.

NoAck

0001 0101

Last host command was not successful.

8.4 INTERRUPT PROCESSING

Unexpected states encountered during run-time, for ex-

ample overrun of the FIFO buffer, are reported as errors.

When the host receives an interrupt from the LM8333, it

uses a READ_INT command to read the interrupt code. If

the code has a set ERROR bit, the host then uses a READ-

_ERROR command to read the error code, as shown in

Figure 11.

www.national.com

12