RL78/G13 CHAPTER 22 SAFETY FUNCTIONS
R01UH0146EJ0100 Rev.1.00 910
Sep 22, 2011
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.
<Control register>
• 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 22-8. 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 starting at the lower RAM address
1 0 The 256 bytes starting at the lower RAM address
1 1 The 512 bytes starting at the lower RAM address
Note The RAM start address differs depending on the size of the RAM provided with the product.
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