UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 655

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

22.3 HALT MODE
22.3.1 HALT Mode Setting and Operating States
mode setting is therefore performed by means of the “MOV STBC, #byte” instruction.
released). Otherwise, several instructions may be executed after the HALT mode has been released and before the interrupt
is acknowledged. This may change the sequential relation between interrupt processing and instruction execution, and
cause a problem.
The HALT mode is selected by setting (1) the HLT bit of the standby control (STBC) register.
The only writes that can be performed on the STBC are 8-bit data writes by means of a dedicated instruction. HALT
Write an NOP instruction three times after the instruction that has set the HALT mode (or after the HALT mode has been
Caution If HALT mode setting is performed when a condition that releases HALT mode is in effect, HALT mode
* Macro service processing is executed.
is not entered, and execution of the next instruction, or a branch to a vectored interrupt service
program, is performed. To ensure that a definite HALT mode setting is made, interrupt requests should
be cleared (0), etc. before entering HALT mode.
Clock oscillator
Internal system clock
CPU
I/O lines
Peripheral functions
Internal RAM
Bus lines
RD, WR output
ASTB output
REFRQ output
HLDRQ input
HLDAK output
Table 22-1 Operating States in HALT Mode
AD0 to AD7
A8 to A19
CHAPTER 22 STANDBY FUNCTION
Operating
Operating
Operation stopped*
Retain state prior to HALT mode setting
Continue operating
Retained
High-impedance
Retained
High level
Low level
Continue operating
Continue operating (input)
Continue operating
615