33742 datasheet(34/65 Pages) FREESCALE

34 / 65 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

33742

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

Figure 20. CAN Interface Levels

TXD AND RXD PINS

The TXD pin has an internal pullup to V2. The state of TXD

depends on the V2 status. RXD is a push-pull structure,

supplied by V2. When V2 is set at 5.0 V and CAN is TXRX

mode, RXD reports bus status. For details, refer to Table 7,

page 25, Table 9, below, and Table 10, page 35.

CAN TXRX MODE AND SLEW RATE SELECTION

The slew rate selection is done via CAN register (refer to

Tables 21 through 23 on page 45). Four slew rates are

available and control the recessive-to-dominant and

dominant-to-recessive transitions. The delay time from TXD

pin to CAN bus, from CAN bus to RXD, and from the TXD to

RXD loop time is affected by the slew rate selection.

CANH

TXD

RXD

Typ 2.5 V

CANL

CAN Recessive State

CAN Dominant State

CAN Recessive State

Typ 2.5 V

VCANH-VCANL > 900 mV

VCANH-VCANL < 500 mV

Table 9. CAN Interface/33742S Modes and Pin Status—Operation with Ballast on V2 (44)

Mode

CAN Mode

(Controlled by SPI)

V2 Voltage

TXD Pin

RXD Pin

CANH/CANL

(Disconnected from

Other Node)

CAN

Communication

Unpowered

–

0.0 V

LOW

Floating to GND

Reset (with Ballast)

–

0.0 V

LOW

Floating to GND

Normal Request

(with Ballast)

–

0.0 V

LOW

Floating to GND

Normal

Sleep

5.0 V

0.0 V

5.0 V

Floating to GND

Normal

Slew Rate 0, 1, 2, 3

5.0 V

Internal Pullup

to V2

Report Bus State

HIGH if Bus

Recessive,

LOW if dominant

Bus Recessive

CANH = CANL = 2.5 V

YES

Standby with

External Ballast

Normal or Sleep

0.0 V

LOW

Floating to GND

Sleep

0.0 V

LOW

Floating to GND

NO.

Wake-up if enabled

Stop

Sleep

0.0 V

LOW

Floating to GND

NO.

Wake-up if enabled

Notes

44.

33742 Datasheet(PDF) 34 Page - Freescale Semiconductor, Inc

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