SC312XDP512F0MPVR datasheet(427/1348 Pages) FREESCALE

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Chapter 10 Freescale’s Scalable Controller Area Network (S12MSCANV3)

MC9S12XDP512 Data Sheet, Rev. 2.21

Freescale Semiconductor

427

Read: Anytime

Write: Anytime when INITRQ = 1 and INITAK = 1, except CANE which is write once in normal and

anytime in special system operation modes when the MSCAN is in initialization mode (INITRQ = 1 and

INITAK = 1).

76543210

CANE

CLKSRC

LOOPB

LISTEN

BORM

WUPM

SLPAK

INITAK

Reset:

00010001

= Unimplemented

Figure 10-5. MSCAN Control Register 1 (CANCTL1)

Table 10-2. CANCTL1 Register Field Descriptions

Field

Description

CANE

MSCAN Enable

0 MSCAN module is disabled

1 MSCAN module is enabled

CLKSRC

MSCAN Clock Source — This bit deﬁnes the clock source for the MSCAN module (only for systems with a clock

generation module; Section 10.4.3.2, “Clock System,” and Section Figure 10-43., “MSCAN Clocking Scheme,”).

0 MSCAN clock source is the oscillator clock

1 MSCAN clock source is the bus clock

LOOPB

Loopback Self Test Mode — When this bit is set, the MSCAN performs an internal loopback which can be used

for self test operation. The bit stream output of the transmitter is fed back to the receiver internally. The RXCAN

input pin is ignored and the TXCAN output goes to the recessive state (logic 1). The MSCAN behaves as it does

normally when transmitting and treats its own transmitted message as a message received from a remote node.

In this state, the MSCAN ignores the bit sent during the ACK slot in the CAN frame acknowledge ﬁeld to ensure

proper reception of its own message. Both transmit and receive interrupts are generated.

0 Loopback self test disabled

1 Loopback self test enabled

LISTEN

Listen Only Mode — This bit conﬁgures the MSCAN as a CAN bus monitor. When LISTEN is set, all valid CAN

messages with matching ID are received, but no acknowledgement or error frames are sent out (see

Section 10.4.4.4, “Listen-Only Mode”). In addition, the error counters are frozen. Listen only mode supports

applications which require “hot plugging” or throughput analysis. The MSCAN is unable to transmit any

messages when listen only mode is active.

0 Normal operation

1 Listen only mode activated

BORM

Bus-Off Recovery Mode — This bits conﬁgures the bus-off state recovery mode of the MSCAN. Refer to

Section 10.5.2, “Bus-Off Recovery,” for details.

0 Automatic bus-off recovery (see Bosch CAN 2.0A/B protocol speciﬁcation)

1 Bus-off recovery upon user request

WUPM

Wake-Up Mode — If WUPE in CANCTL0 is enabled, this bit deﬁnes whether the integrated low-pass ﬁlter is

applied to protect the MSCAN from spurious wake-up (see Section 10.4.5.4, “MSCAN Sleep Mode”).

0 MSCAN wakes up on any dominant level on the CAN bus

1 MSCAN wakes up only in case of a dominant pulse on the CAN bus that has a length of Twup

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