LM8322 datasheet(11/42 Pages) NSC

No. de pieza	LM8322

Descripción Electrónicos	Mobile I/O Companion Supporting Key-Scan, I/O Expansion, PWM, and ACCESS.bus Host Interface

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Fabricante Electrónico	NSC [National Semiconductor (TI)]

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10.4 DEVICE CONFIGURATION AFTER RESET

After the LM8322 has completed its reset initialization, it will

have the following internal configuration:

•

PWM Clock — the PWM clock source is the on-chip clock

divided by 64. This remains in effect until changed by a

host command.

•

Keypad Size — 3 × 3.

•

Digital Multiplexers — disabled.

•

IRQ — enabled, active low.

•

NOINIT Bit — set.

•

Debounce Time — 3 scan cycles (about 12 milliseconds).

•

Active Time — 500 milliseconds.

10.5 CONFIGURATION INPUTS

The states sampled from the CONFIG_1 and CONFIG_2 in-

puts during reset select the ACCESS.bus address used by

the LM8322, as shown in Table 4. The address occupies the

high seven bits of the first byte of a bus transaction, with the

LSB (shown as X below) indicating the direction of transfer.

TABLE 4. Bus Address Selection

CONFIG_1

CONFIG_2

Bus Address

0

1000 010X

0

1

1000 011X

1

0

1000 100X

1

1000 101X

When these pins are used as GPIO ports, the design must

ensure that they have the desired states during reset. For ex-

ample, a 100-kohm resistor to ground can impose a logic 0

during reset without interfering with normal operation as a

GPIO port.

10.6 INITIALIZATION

The LM8322 waits for a WRITE_CFG command from the

host. During this time, IRQ is asserted to request service from

the host. Figure 3 describes the behavior of the LM8322 fol-

lowing reset.

30013603

FIGURE 3. LM8322 Initialization Behavior

Figure 4 shows the timing of IRQ relative to a RESET or POR

event and the WRITE_CFG command. 100 µs after a RE-

SET or POR event, IRQ is asserted and any READ_INT

command will return an interrupt code with the NOINIT bit set.

90 µs after a WRITE_CFG command is received, IRQ is de-

asserted.

30013604

FIGURE 4. IRQ Reset Timing

11

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LM8322 Datasheet(PDF) 11 Page - National Semiconductor (TI)

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