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Renesas rl78 User Manual

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RL78/G1A 
CHAPTER  22   SAFETY  FUNCTIONS 
22.3.4  RAM guard function 
In order to guarantee safety during operation, the IEC61508 standard mandates that important data stored in the RAM 
be protected, even if the CPU freezes. 
This RAM guard function is used to protect data in the specified memory space. 
If the RAM guard function is specified, writing to the specified RAM space is disabled, but reading from the space can 
be carried out as usual. 
 
22.3.4.1  Invalid memory access detection control register (IAWCTL) 
This register is used to control the detection of invalid memory access and RAM/SFR guard function. 
GRAM1 and GRAM0 bits are used in RAM guard function. 
The IAWCTL register can be set by an 8-bit memory manipulation instruction. 
Reset signal generation clears this register to 00H. 
 
Figure 22-9.  Format of Invalid Memory Access Detection Control Register (IAWCTL) 
 
Address: F0078H     After reset: 00H     R/W 
Symbol 
7 6 5 4 3 2 1 0 
IAWCTL 
IAWEN  0 GRAM1 
GRAM0 0 GPORT 
GINT 
GCSC 
 
GRAM1 GRAM0 
RAM 
guard 
space
Note 
 
0 
0 
Disabled.  RAM can be written to. 
0 
1 
The 128 bytes of space starting at the start address in the RAM 
1 
0 
The 256 bytes of space starting at the start address in the RAM 
1 
1 
The 512 bytes of space starting at the start address in the RAM 
<R> 
<R> 
<R> 
 
Note  The RAM start address differs depending on the size of the RAM provided with the product. 
 
R01UH0305EJ0200  Rev.2.00 
 
 
780  
Jul 04, 2013