33742 datasheet(26/65 Pages) FREESCALE

26 / 65 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

33742

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

APPLICATION WAKE-UP FROM THE 33742

When the application is in Stop mode, it can be awakened

from the SBC side. When a wake-up condition is detected by

the SBC (for example, CAN, wake-up input), the 33742

enters the Normal Request mode and generates an interrupt

pulse at the INT pin.

APPLICATION WAKE-UP FROM THE MCU

When the device is in the Stop mode, a wake-up event

may come from the system MCU. In this case the MCU

selects the device the using a LOW-to-HIGH transition on the

33742 CS pin. Then the 33742S goes into Normal Request

mode and generates an interrupt pulse at the INT pin.

STOP MODE CURRENT MONITOR

If the VDD output current exceeds an internal set threshold

(IDDS-WU), the SBC automatically enters the Normal Request

mode and generates an interrupt at the INT pin. The interrupt

is a non-maskable and the INTR register will have no flag set.

INTERRUPT GENERATION WHEN WAKE-UP

FROM STOP MODE

When the SBC wakes from Stop mode, it first enters the

Normal Request mode before generating a 10

µs typical

pulse on the INT pin. These are non-maskable interrupts with

the wake-up event read through the SPI registers, the

CANWU bit in the CAN Register (CANR), or the LCTRx bit in

the Wake-Up Register (WUR). In case of wake-up from Stop

mode overcurrent situation or from forced wake-up, no bits

are set. After the INT pulse, the 33742 accepts SPI command

after a time delay (tS-1STSPI).

WATCHDOG SOFTWARE IN STOP MODE

If the SBC watchdog is enabled, the application must

provide a “system ok” response before the end of the 33742

watchdog time. Typically an MCU initiates the wake-up of the

33742 through the SPI wake-up (CS activation). The SBC will

awaken and jump into the Normal Request mode. The MCU

has to configure the 33742 to go to either Normal or Standby

mode. The MCU can then decide to return to the Stop mode.

If no MCU wake-up occurs within the watchdog time

period, the SBC activates the RST pin and jumps into the

Normal Request mode. The MCU can then be re-initialized.

STOP MODE ENTER COMMAND

Stop mode is entered at the end of the SPI message at the

rising edge of the CS. (Refer to the t CS-STOP data in the

Dynamic Electrical Characteristics table on page 17.) Once

Stop mode is entered, the SBC can wake up from a VDD

regulator overcurrent detection state. In order to allow time

for the MCU to complete the last CPU instruction and enter

its low power mode, a deglitcher time of 40

µs typical is

implemented.

Figure 11, page 27, depicts the operation of entering the

Stop mode.

Stop

VDD: ON

(Limited Current

Capability),

V2: OFF,

HS:OFF or Cyclic Sense

CAN, SPI, L0:L3,

Cyclic Sense,

Forced Wake-Up,

IDD Overcurrent (39)

Normally HIGH.

Active LOW if WDOG

(40)

or VDD undervoltage

occurs

Signal 33742S

wake-up and

IDD > IDDS-WU

(not maskable)

Running if

enabled.

Not running if

disabled

Low power.

Wake-up capability

if enabled

Sleep

VDD: OFF,

V2: OFF,

HS: OFF or Cyclic

CAN, SPI,

L0:L3, Cyclic Sense

Forced Wake-Up

LOW

Not Active

Not running

Low power.

Wake-up capability

if enabled

Normal

Debug (38)

Same as Normal

–

Normally HIGH.

Active LOW if VDD

undervoltage occurs

Same as Normal

Not running

Same as Normal

Standby

Debug (38)

Same as Standby

–

Normally HIGH.

Active LOW if VDD

undervoltage occurs

Same as Standby Not running

Same as Standby

Stop

Debug (38)

Same as Stop

Normally HIGH.

Active LOW if VDD

undervoltage occurs

Same as Stop

Not running

Same as Stop

Flash

Programming

Forced externally

–

Not operating

Notes

38.

Mode entered via special sequence described under the heading Debug Mode: Hardware and Software Debug with the 33742 beginning

on page 30.

39.

IDD overcurrent always enabled.

40.

WDOG if enabled.

33742 Datasheet(PDF) 26 Page - Freescale Semiconductor, Inc

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