KOYO|CPU BUS|CPU Module
Description
PXB-721 is a CPU module designed to manage all aspects of system control, including communication with specialty and remote I/O modules via the CPU bus. It ensures efficient data transfer between the CPU and connected modules during each scan cycle.
Features
- CPU Bus Communication: Direct communication with specialty modules over the backplane's CPU bus.
- Real-Time Clock Update: Updates internal clock and calendar timers.
- Watchdog Timer Control: Monitors and resets the watchdog timer for system stability.
- Diagnostics: Performs system diagnostics and reports error conditions.
Technical Specifications
CPU Bus Communication
- Specialty modules can communicate directly with the CPU via the CPU bus.
- Time required depends on the type of modules installed and the type of request processed.
- Example: High-Speed Counter module for pulse counting at high rates.
- Note: Some specialty modules can significantly impact CPU scan time.
Update Clock/Calendar, Special Relays, Special Registers
- Internal real-time clock and calendar are updated and loaded into special V-memory locations.
- This update occurs during both Run and Program Modes.
- Example: Updating special relays and diagnostic relays.
Write Outputs to Specialty and Remote I/O
- After updating outputs in local and expansion bases, the CPU sends output point information to any installed specialty modules.
- Example: Writing output status from the image register to Remote I/O racks.
- Note: Remote I/O Master module updates actual remote modules during the next communication sequence.
Scan Time Considerations
- Scan time covers all cyclical tasks performed by the operating system.
- Minimum, maximum, and current scan times can be viewed using DirectSOFT or Handheld Programmer.
- Default watchdog timer value: 200ms.
- If exceeded, CPU enters Program Mode, turns off all outputs, and reports an error (e.g., "E003 S/W TIMEOUT").
- Use AUX 53 to view scan times and AUX 55 to adjust watchdog timer value.
Timing Factors
- Overhead times for different CPUs:
- D2-230: 66.0 µs
- D2-240: 33.0 µs
- D2-250–1: 28.1 µs
- D2-260/D2-262: 28.1 µs
- Per output point times:
- D2-230: 8.5 µs
- D2-240: 14.6 µs
- D2-250–1: 3.0 µs
- D2-260/D2-262: 3.0 µs
Example Calculation for Output Update Time
- For D2-240 writing data for two 8-point output modules:
- Formula: Time = 33 + (NO x 14.6 µs)
- Example: Time = 33 + (16 x 14.6 µs) = 266.6 µs
KOYO|CPU BUS|CPU Module
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Descriptions
Description
PXB-721 is a CPU module designed to manage all aspects of system control, including communication with specialty and remote I/O modules via the CPU bus. It ensures efficient data transfer between the CPU and connected modules during each scan cycle.
Features
- CPU Bus Communication: Direct communication with specialty modules over the backplane's CPU bus.
- Real-Time Clock Update: Updates internal clock and calendar timers.
- Watchdog Timer Control: Monitors and resets the watchdog timer for system stability.
- Diagnostics: Performs system diagnostics and reports error conditions.
Technical Specifications
CPU Bus Communication
- Specialty modules can communicate directly with the CPU via the CPU bus.
- Time required depends on the type of modules installed and the type of request processed.
- Example: High-Speed Counter module for pulse counting at high rates.
- Note: Some specialty modules can significantly impact CPU scan time.
Update Clock/Calendar, Special Relays, Special Registers
- Internal real-time clock and calendar are updated and loaded into special V-memory locations.
- This update occurs during both Run and Program Modes.
- Example: Updating special relays and diagnostic relays.
Write Outputs to Specialty and Remote I/O
- After updating outputs in local and expansion bases, the CPU sends output point information to any installed specialty modules.
- Example: Writing output status from the image register to Remote I/O racks.
- Note: Remote I/O Master module updates actual remote modules during the next communication sequence.
Scan Time Considerations
- Scan time covers all cyclical tasks performed by the operating system.
- Minimum, maximum, and current scan times can be viewed using DirectSOFT or Handheld Programmer.
- Default watchdog timer value: 200ms.
- If exceeded, CPU enters Program Mode, turns off all outputs, and reports an error (e.g., "E003 S/W TIMEOUT").
- Use AUX 53 to view scan times and AUX 55 to adjust watchdog timer value.
Timing Factors
- Overhead times for different CPUs:
- D2-230: 66.0 µs
- D2-240: 33.0 µs
- D2-250–1: 28.1 µs
- D2-260/D2-262: 28.1 µs
- Per output point times:
- D2-230: 8.5 µs
- D2-240: 14.6 µs
- D2-250–1: 3.0 µs
- D2-260/D2-262: 3.0 µs
Example Calculation for Output Update Time
- For D2-240 writing data for two 8-point output modules:
- Formula: Time = 33 + (NO x 14.6 µs)
- Example: Time = 33 + (16 x 14.6 µs) = 266.6 µs
