USBB17RX78K4-XXX NEC Electronics, USBB17RX78K4-XXX Datasheet - Page 31

• Manufacturer Part Number: USBB17RX78K4-XXX
• Description: 78K/4 series realtime OS
• Manufacturer: NEC Electronics

3.1 RX78K/IV Configuration
3.1.1 Flow of overall processing
multiple tasks can be allocated to register bank 1, and one task each to register bank 2 to 7.
unnecessary to save the registers when tasks are switched over during execution.
interrupt handler uses the stack area of the task being performed when an interrupt occurred.
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RX78K/IV uses register bank 0 of the 8 register banks of the 78K/IV series microcomputers. For user tasks,
The tasks allocated to register banks 2 to 7 can realize high-speed task switching, because with them, it is
An example method for allocating register banks is shown below.
Example 1: With 6 tasks
Example 2: With 6 tasks
Example 3: With 10 tasks
The task area is required for each task; therefore, when performing a task, the stack area of the task is used. The
The stack state in dispatching is shown below.
High
Low
Register bank 1
Register banks 2 to 7 : One task each
Register bank 1
Register banks 2 to 4 : One task each
Register banks 5 to 7 : For interrupting
Register bank 1
Register banks 2 to 7 : One task each
When tasks are allocated to register bank 1
CHAPTER 3
PC15-8
PSWH
R15
R13
R
Stack area
RX78K/IV BASIC OPERATIONS AND CONTROL BLOCKS
PC19-16
: None
: 3 tasks
: 4 tasks
PC7-0
PSWL
Fig. 3-1 Stack State in Dispatching
R14
R2
R0
High
Low
When tasks are allocated to register bank 2 to 7
PC15-8
PSWH
Stack area
PC19-16
PC7-0
PSWL