33993 datasheet(17/28 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33993

FUNCTIONAL DEVICE OPERATION

LOGIC COMMANDS AND REGISTERS

EXAMPLE OF NORMAL MODE OPERATION

The operation of the device in Normal Mode is defined by

the states of the programmable internal control registers. A

typical application may have the following settings:

• Programmable Switch – Set to Switch-to-Ground

• All Inputs Set as Wake-Up

• Wetting Current On (16 mA)

• Wetting Current Timer On (20 ms)

• All inputs Tri-State-Disabled (comparator is active)

• Analog select 00000 (no input channel selected)

With the device programmed as above, an interrupt will be

generated with each switch contact change of state (open-to-

close or close-to-open) and 16 mA of contact wetting current

will be source for 20 ms. The INT pin will remain low until

switch status is acknowledged by the microprocessor. It is

critical to understand INT will not be cleared on the rising

edge of CS if a switch closure occurs while CS is low. The

maximum duration a switch state change can exist without

acknowledgement depends on the software response time to

the interrupt. Figure 4, page 8, shows the interaction

between changing input states and the INT and CS pins.

If desired the user may disable interrupts (wake up/

interrupt command) from the 33993 device and read the

switch states on a periodic basis. Switch activation and

deactivation faster than the MCU read rate will not be

acknowledged.

The 33993 device will exit the Normal mode and enter the

Sleep mode only with a valid sleep command.

SLEEP MODE

Sleep mode is used to reduce system quiescent currents.

Sleep mode may be entered only by sending the sleep

command. All register settings programmed in Normal mode

will be maintained in Sleep mode.

The 33993 will exit Sleep mode and enter Normal mode

when any of the following events occur:

• Input Switch Change of State (when enabled)

• Interrupt Timer Expire

• Falling Edge of WAKE

• Falling Edge of INT (with VDD = 5.0 V and WAKE at

Logic [1])

• Falling Edge of CS (with VDD = 5.0 V)

• Power-ON Reset (POR)

The VDD supply may be removed from the device during

Sleep mode. However removing VDD from the device in

Sleep mode will disable a wake-up from falling edge of INT

and CS.

Note In cases where CS is used to wake the device, the

first SO data message is not valid.

The sleep command contains settings for two

programmable timers for Sleep mode, the interrupt timer and

the scan timer, as shown in Table 17.

The interrupt timer is used as a periodic wake-up timer.

When the timer expires, an interrupt is generated and the

device enters Normal mode. Table 18 shows the

programmable settings of the Interrupt timer.

Table 15. Serial Output (SO) Bit Data

Type of Input

Input

Programmed

Voltage on

Input Pin

SO SPI Bit

Switch to

Ground

SPn < 4.0 V

Switch to

Ground

SPn > 4.0 V

Switch to

Battery

SPn < 4.0 V

Switch to

Battery

SPn > 4.0 V

N/A

SGn < 4.0 V

N/A

SGn > 4.0 V

Table 15. Serial Output (SO) Bit Data

Type of Input

Input

Programmed

Voltage on

Input Pin

SO SPI Bit

Table 16. Serial Output (SO) Response Register

SO Response Will

Always Send

them

flg

int

flg

SP7 SP6 SP5 SP4 SP3 SP2 SP1 SP0

SG1

SG9 SG8 SG7 SG6 SG5 SG4 SG3 SG2 SG1 SG0

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