UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 551

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

20.3.6 Program Status Word (PSW)
IE flag that sets enabling/disabling of maskable interrupts is mapped in the low-order 8 bits of the PSW (PSWL).
instruction or dedicated instruction (EI/DI).
flag is cleared (0). PSWL is also saved to the stack by the PUSH PSW instruction, and is restored from the stack by the
RETI, RETB and POP PSW instructions.
the IE flag is cleared (0). PSWL is restored from the fixed area in the register bank by an RETCSI or RETCSB instruction.
20.4 SOFTWARE INTERRUPT ACKNOWLEDGMENT OPERATIONS
be disabled.
20.4.1 BRK Instruction Software Interrupt Acknowledgment Operation
the stack, the IE flag is cleared (0), the vector table (003EH/003FH) contents are loaded into the low-order 16 bits of the
PC, and 0000B into the high-order 4 bits, and a branch is performed (the start of the service program must be in the base
area).
The PSW is a register that holds the current status regarding instruction execution results and interrupt requests. The
PSWL can be read or written to with an 8-bit manipulation instruction, and can also be manipulated with a bit manipulation
When a vectored interrupt is acknowledged or a BRK instruction is executed, PSWL is saved to the stack and the IE
When context switching or a BRKCS instruction is executed, PSWL is saved to a fixed area in the register bank, and
RESET input clears PSWL to 80H.
A software interrupt is acknowledged in response to execution of a BRK or BRKCS instruction. Software interrupts cannot
When a BRK instruction is executed, the program status word (PSW), program counter (PC) are saved in that order to
The RETB instruction must be used to return from a BRK instruction software interrupt.
Caution The RETI instruction must not be used to return from a BRK instruction software interrupt.
PSWL
S
7
6
Z
RSS
5
Figure 20-6 Program Status Word (PSWL) Format
AC
4
CHAPTER 20 INTERRUPT FUNCTIONS
IE
3
P/V
2
1
0
CY
0
Used in normal instruction execution
On Reset
IE
0
1
00H
Interrupt Acknowledgment
Enabling/Disabling
Disabled
Enabled
511