32176 Datasheet, PDF (617/742 Pages) Renesas Technology Corp – 32-BIT RISC SINGLE-CHIP MICROCOMPUTER

17
RAM BACKUP MODE
17.4 Exiting RAM Backup Mode (Wakeup)
17.4 Exiting RAM Backup Mode (Wakeup)
The processing to place the M32R/ECU out of RAM backup mode and return it to normal operation mode is
referred to as “wakeup” processing. Figure 17.4.1 shows an example of wakeup processing.
Wakeup processing is initiated by applying a reset. The following shows how to execute wakeup processing.
(1) Reset the microcomputer ((a) in Figure 17.4.1).
(2) Set port n for output mode and output a "H" from the port ((b) in Figure 17.4.1) (Note 1)
(3) Compare the RAM content against the RAM check data created before entering RAM backup mode ((c) in
Figure 17.4.1).
(4) If the comparison in (3) did not match, initialize the RAM ((d) in Figure 17.4.1).
If the comparison in (3) matched, use the retained data in the program.
(5) Initialize each internal circuit ((e) in Figure 17.4.1) before returning to the main routine ((f) in Figure 17.4.1).
Note 1: For wakeup from power outage RAM backup mode, port n settings are unnecessary.
Example of wakeup processing
(a)
Reset
(b)
Set the transistor's base
connecting pin (port n)
for "H" level output mode
(Note 1)
Compare RAM content
OK
(c)
against backup RAM
check data
Error
(d)
Initialize the RAM
(e)
Initialize each circuit
(f)
To the main routine
Note 1: For wakeup from power outage RAM backup mode, port n settings are unnecessary.
Figure 17.4.1 Wakeup Processing
32176 Group Hardware Manual
Rev.1.10 REJ09B0067-0110 Jun 20.06
17-9