PC912XDP512F0MPVR datasheet(467/1348 Pages) FREESCALE

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

MC9S12XDP512 Data Sheet, Rev. 2.21

Freescale Semiconductor

467

10.4.4.3

Emulation Modes

In all emulation modes, the MSCAN module behaves just like normal system operation modes as

described within this speciﬁcation.

10.4.4.4

Listen-Only Mode

In an optional CAN bus monitoring mode (listen-only), the CAN node is able to receive valid data frames

and valid remote frames, but it sends only “recessive” bits on the CAN bus. In addition, it cannot start a

transmision. If the MAC sub-layer is required to send a “dominant” bit (ACK bit, overload ﬂag, or active

error ﬂag), the bit is rerouted internally so that the MAC sub-layer monitors this “dominant” bit, although

the CAN bus may remain in recessive state externally.

10.4.4.5

Security Modes

The MSCAN module has no security features.

10.4.5

Low-Power Options

If the MSCAN is disabled (CANE = 0), the MSCAN clocks are stopped for power saving.

If the MSCAN is enabled (CANE = 1), the MSCAN has two additional modes with reduced power

consumption, compared to normal mode: sleep and power down mode. In sleep mode, power consumption

is reduced by stopping all clocks except those to access the registers from the CPU side. In power down

mode, all clocks are stopped and no power is consumed.

Table 10-36 summarizes the combinations of MSCAN and CPU modes. A particular combination of

modes is entered by the given settings on the CSWAI and SLPRQ/SLPAK bits.

For all modes, an MSCAN wake-up interrupt can occur only if the MSCAN is in sleep mode (SLPRQ = 1

and SLPAK = 1), wake-up functionality is enabled (WUPE = 1), and the wake-up interrupt is enabled

(WUPIE = 1).

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