4513_03 Datasheet, PDF (163/210 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.9 RAM back-up
Table 2.9.2 Return source and return condition
Return source
Return condition
Remarks
Ports P0, P1
Return by an external falling Set the port using the key-on wakeup function selected
edge input (“H”→“L”).
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.
Port P30/INT0 Return by an external “H” level Select the return level (“L” level or “H” level) with the bit
or “L” level input.
2 of register I1 according to the external state before
Port P31/INT1
The EXF0 flag is not set. going into the RAM back-up state.
Return by an external “H” level Select the return level (“L” level or “H” level) with the bit
or “L” level input.
2 of register I2 according to the external state before
The EXF1 flag is not set. going into the RAM back-up state.
(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
Return condition
P flag
External wakeup signal input
1
Reset
0
Software start
P = “1” ^Yes
?
No
Cold start
Warm start
Fig. 2.9.1 Start condition identified example
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 P00–P03, P10–P13.
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 : 00002 at RAM back-up : state retained
Pins P12 and P13 key-on wakeup 0 Key-on wakeup not used
K03
control bit
1 Key-on wakeup used
Pins P10 and P11 key-on wakeup 0 Key-on wakeup not used
K02
control bit
1 Key-on wakeup used
Pins P02 and P03 key-on wakeup 0 Key-on wakeup not used
K01
control bit
1 Key-on wakeup used
Pins P00 and P01 key-on wakeup 0 Key-on wakeup not used
K00
control bit
1 Key-on wakeup used
Note: “R” represents read enabled, and “W” represents write enabled.
R/W
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4513/4514 Group User’s Manual