UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 651

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

22.2 CONTROL REGISTERS
22.2.1 Standby Control Register (STBC)
a dedicated instruction. This dedicated instruction, MOV STBC, #byte, has a special code configuration (4 bytes), and a
write is only performed if the 3rd and 4th bytes of the operation code are mutual 1’s complements.
error interrupt is generated. In this case, the return address saved in the stack area is the address of the instruction that
was the source of the error, and thus the address that was the source of the error can be identified from the return address
saved in the stack area.
RA78K4, only the correct dedicated instruction is generated when MOV STBC, #byte is written), system initialization should
be performed by the program.
operation. That is, a write is not performed to the STBC, and an interrupt such as an operand error interrupt is not generated.
The STBC is used to select the STOP mode setting and the internal system clock.
To prevent entry into standby mode due to an inadvertent program loop, the STBC register can only be written to with
If the 3rd and 4th bytes of the operation code are not mutual 1’s complements, a write is not performed and an operand
If recovery from an operand error is simply performed by means of an RETB instruction, an endless loop will result.
As an operand error interrupt is only generated in the event of an inadvertent program loop (with the NEC assembler,
Other write instructions (MOV STBC, A; AND STBC, #byte; SET1 STBC.7, etc.) are ignored and do not perform any
The STBC can be read at any time by a data transfer instruction.
RESET input sets the STBC register to 30H.
The format of the STBC is shown in Figure 22-3.
CHAPTER 22 STANDBY FUNCTION
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