RL78/G1H CHAPTER 24 SAFETY FUNCTIONS
R01UH0575EJ0120 Rev. 1.20 Page 785 of 920
Dec 22, 2016
24.3.4 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.
24.3.4.1 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 24 - 9 Format of Invalid memory access detection control register (IAWCTL)
Note The RAM start address differs depending on the size of the RAM provided with the product.
Address: F0078H After reset: 00H R/W
Symbol76543210
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 starting at the start RAM address
1 0 The 256 bytes starting at the start RAM address
1 1 The 512 bytes starting at the start RAM address
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