MC33390D/DR2 View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

MC33390D/DR2

Class B Serial Transceiver

Motorola => Freescale 

Freescale Semiconductor, Inc.

Receiver Protocol

The Class B communication scheme uses a variable pulse

width (VPW) protocol. The microcontroller provides the VPW

decoding function. Once the receiver detects a transition on Rx,

it starts an internal counter. The initial “start of frame” bit is a

logic [1] and lasts 200 µs. For subsequent bits, if there is a bus

transition before 96 µs, one logic state is inferred. If there is a

bus transition after 96 µs, the other logic state is inferred. The

“end of data” bit is a logic [0] and lasts 200 µs. If there is no

activity on the bus for 280 µs to 320 µs following a broadcast

message, multiple unit nodes may arbitrate for control of the

next message. During an arbitration, after the “start of frame” bit

has been transmitted, the secondary node transmitting the

most consecutive logic [0] bits will be granted sole transmission

access to the bus for that message.

Loss of Assembly Ground Connection

The definition of a loss of assembly ground condition at the

device level is that all pins of the 33390, with the exception of

BUS and LOAD, see a very low impedance to VBAT.

The LOAD pin of the device has an internal transistor switch

connected to it that is normally saturated to ground. This pulls

the LOAD-side of the external resistor (tied from BUS to LOAD)

to ground under normal conditions. The LOAD pin switch is

essentially that of an “upside down” FET, which is normally

biased “on” so long as module ground is present and biased

“off” when loss-of-ground occurs. When a loss of assembly

ground occurs, the load transistor switch is self-biased “off”,

allowing no more than 100 µA of leakage current to flow in the

LOAD pin. During such a loss of assembly ground condition, the

BUS and LOAD pins exhibit a high impedance to VBAT; all other

pins will exhibit a low impedance to VBAT. During this condition

the BUS pin is prevented from sourcing any current or loading

the bus, which would cause a corruption of any data being

transmitted on the bus. While a particular assembly is

experiencing a loss of ground, all other assembly nodes are

permitted to function normally. It should be noted that with other

nodes existing on the bus, the bus will always have some

minimum/maximum impedance to ground as shown in Table 1,

page 10.

Loss of Assembly Battery Connection

The definition of a loss of assembly battery condition at the

device level is that the VBAT pin of the 33390 sees an infinite

impedance to VBAT, but there is some undefined impedance

between these pins and ground.

MOTOROLA ANALOG INTEGRATED CIRFCoUIrTMDEoVrICeEIDnAfoTArmation On This Product,

Go to: www.freescale.com

33390

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