MC68HC08AS32 Datasheet, PDF (368/394 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

Byte Data Link Controller-Digital (BDLC-D)
20.8 Low-Power Modes
The following information concerns wait mode and stop mode.
20.8.1 Wait Mode
This power-conserving mode is entered automatically from run mode
whenever the CPU executes a WAIT instruction and the WCM bit in
BDLC control register 1 (BCR1) is previously clear. In BDLC wait mode,
the BDLC cannot drive any data.
A subsequent successfully received message, including one that is in
progress at the time that this mode is entered, will cause the BDLC to
wake up and generate a CPU interrupt request if the interrupt enable (IE)
bit in the BDLC control register 1 (BCR1) is previously set. (See 20.7.2
BDLC Control Register 1 for a better understanding of IE.) This results
in less of a power saving, but the BDLC is guaranteed to receive
correctly the message which woke it up, since the BDLC internal
operating clocks are kept running.
NOTE: Ensuring that all transmissions are complete or aborted before putting
the BDLC into wait mode is important.
20.8.2 Stop Mode
This power-conserving mode is entered automatically from run mode
whenever the CPU executes a STOP instruction or if the CPU executes
a WAIT instruction and the WCM bit in the BDLC control register 1
(BCR1) is previously set. This is the lowest power mode that the BDLC
can enter.
A subsequent passive-to-active transition on the J1850 bus will cause
the BDLC to wake up and generate a non-maskable CPU interrupt
request. When a STOP instruction is used to put the BDLC in stop mode,
the BDLC is not guaranteed to correctly receive the message which
woke it up, since it may take some time for the BDLC internal operating
clocks to restart and stabilize. If a WAIT instruction is used to put the
BDLC in stop mode, the BDLC is guaranteed to correctly receive the
byte which woke it up, if and only if an end-of-frame (EOF) has been
Advance Information
368
Byte Data Link Controller-Digital (BDLC-D)
MC68HC08AS32 — Rev. 3.0
MOTOROLA