Renesas 4514 - Manual (Page 163)

APPLICATION
2-60 4513/4514 Group User’s Manual
2.9 RAM back-up
Remarks
Set the port using the key-on wakeup function selected
with register K0 to “H” level before going into the RAM
back-up state because the port P0 shares the falling
edge detection circuit with port P1.
Select the return level (“L” level or “H” level) with the bit
2 of register I1 according to the external state before
going into the RAM back-up state.
Select the return level (“L” level or “H” level) with the bit
2 of register I2 according to the external state before
going into the RAM back-up state.
Return condition
Return by an external falling
edge input (“H”
→
“L”).
Return by an external “H” level
or “L” level input.
The EXF0 flag is not set.
Return by an external “H” level
or “L” level input.
The EXF1 flag is not set.
Table 2.9.2 Return source and return condition
(2) Start condition identification
When system returns from both RAM back-up mode and reset, software is started from address 0
in page 0.
The start condition (warm start or cold start) can be identified by examining the state of the power
down flag (P) with the SNZP instruction.
Table 2.9.3 Start condition identification
Fig. 2.9.1 Start condition identified example
Return source
Ports P0, P1
Port P3 0 /INT0
Port P3 1 /INT1
External wakeup
signal
Return condition
External wakeup signal input
Reset
P flag
1
0
Software start
P = “1”
?
Yes
Warm start
Cold start
No
2.9.2 Related register
(1) Key-on wakeup control register K0
Key-on wakeup control register K0 controls key-on wakeup functions of ports P0 0 –P0 3 , P1 0 –P1 3 .
Set the contents of this register through register A with the TK0A instruction. The TAK0 instruction
can be used to transfer the contents of register K0 to register A.
Table 2.9.4 shows the key-on wakeup control register K0.
Table 2.9.4 Key-on wakeup control register K0
Key-on wakeup control register K0 at reset : 0000 2 at RAM back-up : state retained R/W
Key-on wakeup not used
Key-on wakeup used
Key-on wakeup not used
Key-on wakeup used
Key-on wakeup not used
Key-on wakeup used
Key-on wakeup not used
Key-on wakeup used
Pins P1 2 and P1 3 key-on wakeup
control bit
Pins P1 0 and P1 1 key-on wakeup
control bit
Pins P0 2 and P0 3 key-on wakeup
control bit
Pins P0 0 and P0 1 key-on wakeup
control bit
0
1
0
1
0
1
0
1
K0 3
K0 2
K0 1
K0 0
Note: “R” represents read enabled, and “W” represents write enabled.