Renesas RL78 Series User Manual page 765

RL78/G1D
23.3.5 SFR guard function
In order to guarantee safety during operation, the IEC61508 standard mandates that important SFRs be protected from
being overwritten, even if the CPU freezes.
This SFR guard function is used to protect data in the control registers used by the port function, interrupt function,
clock control function, voltage detection function, and RAM parity error detection function.
If the SFR guard function is specified, writing to the specified SFRs is disabled, but reading from the SFRs can be
carried out as usual.
23.3.5.1 Invalid memory access detection control register (IAWCTL)
This register is used to control the detection of invalid memory access and RAM/SFR guard function.
GPORT, GINT and GCSC bits are used in SFR guard function.
The IAWCTL register can be set by an 8-bit memory manipulation instruction.
Reset signal generation clears this register to 00H.
Figure 23-10. Format of Invalid Memory Access Detection Control Register (IAWCTL)
Address: F0078H After reset: 00H
Symbol 7
IAWCTL IAWEN
GPORT
0
1
GINT
0
1
GCSC
0
1
Note Pxx (Port register) is not guarded.
R01UH0515EJ0120 Rev.1.20
Dec 16, 2016
R/W
6 5
0 GRAM1
Disabled. Control registers of port function can be read or written to.
Enabled. Writing to control registers of port function is disabled. Reading is enabled.
[Guarded SFR] PMxx, PUxx, PIMxx, POMxx, PMCxx, ADPC, PIOR
Disabled. Registers of interrupt function can be read or written to.
Enabled. Writing to registers of interrupt function is disabled. Reading is enabled.
[Guarded SFR] IFxx, MKxx, PRxx, EGPx, EGNx
Control registers of clock control function, voltage detector and RAM parity error detection function guard
Disabled. Control registers of clock control function, voltage detector and RAM parity error detection
function can be read or written to.
Enabled. Writing to control registers of clock control function, voltage detector and RAM parity error
detection function is disabled. Reading is enabled.
[Guarded SFR] CMC, CSC, OSTS, CKC, PERx, OSMC, LVIM, LVIS, RPECTL
CHAPTER 23 SAFETY FUNCTIONS
4 3
GRAM0 0
Control registers of port function guard
Registers of interrupt function guard
2 1
GPORT GINT
Note
0
GCSC
744