AP29002
Standalone TwinCAN Controller
Using special features of the 82C900
Application Note
56
V 1.0, 2004-02
3.12
Power Saving Modes
The 82C900 provides two different types of power-saving modes.
If the 82C900 is in Sleep Mode, the TwinCAN, the SSC and the 8-Bit port logic are
gated off. But the clock is still running. So it is possible to wake it up with a falling edge
on /CS, /SLS or /RESET or with CAN messages on node A or B, if the bits CANAWU
or CANBWU in CLKCTR are set. The messages that wakes up the 82C900 won’t get
lost.
If the 82C900 is in Power Down Mode the clock stops working and it can only be
woken up by a /RESET.
The Modes can be entered in different ways. One way is the direct configuration in the
CLKCTR-register via Parallel Interface. There are problems using the SSC to configure
the sleep mode directly in the CLKCTR-register (see errata sheet for details). The
other way is to use one receiving message object with 2 data bytes to configure the
CLKCTR-register. This object is configured in register CANPWD. The first byte of the
received message from SLPMSG must be the SLPCODE and the second byte is
written into the CLKCTR-register.
Table 10
CLKCTR configurations for the Power Saving Modes
PWD=’0’ & CANCLK =’1’
Normal Operation Mode
PWD=’0’ & CANCLK=’1’
Sleep Mode
PWD=’1’ & CANCLK=’X’
Power Down Mode
