2. Programming Concepts AB-phase input high-speed counter: Example: LD M1002 M1002 MOV K2 D1022 LD X20 RST C251 LD X21 DCNT C251 K5 LD C251 OUT Y0 1. When X20 is ON, RST instsruction executes and the current value in C251 will be cleared. Contact C251 will be OFF. 2. When X21 is ON, C251 receives A phase counting signal of X0 input terminal and B phase counting signal of X1 input terminal and executes count up or count down 3. When counter C251 reaches K5, contact C251 will be ON. If there is still input signal from X0 or X1, C251 will keep on counting 4. Counting mode can be specified as double frequency or 4-times frequency by D1022. Default: quadruple frequency.
X20 X21 C251 Y0 X20 A-phase X0 B-phase X1 C251 present value 0 1 2 3 4 5 6 0 1 2 3 4 5 3 Counting up Counting down Y0, C251 contact 2.13 Special Data Register The types and functions of special registers (special D) are listed in the table below. Care should be taken that some registers of the same No. may bear different meanings in different series MPUs. Special M and special D marked with “*” will be further illustrated in 2.13. Columns marked with “R” refers to “read only”, “R/W” refers to “read and write”, “-“ refers to the status remains unchanged and “#” refers to that system will set it up according to the status of the PLC.
For detailed explanation please also refer to 2.13 in this chapter. 2-31 MOV K2 D1022 RST C251 DCNT C251 K5 21 SS2 SA2 SE OFF STOP RUN Special ES2 Latch Content SX2 Attrib. Default D EX2 -ed ON RUN STOP D1000* Setting value of the watchdog timer (WDT) (Unit: 1ms) ○ ○ ○ ○ 200 - - R/W NO 200 D1001 Displaying the firmware version of DVP- PLC (For example, the firmware version is 1.0 if the value in D1001 is HXX10.) ○ ○ ○ ○ - - - R NO # D1002* Program capacity (ES2/EX2/SA2/SX2: 15872; SS2: 7920) ○ ○ ○ ○ # - - R NO # D1003 Sum of the PLC internal program memory (ES2/EX2/SA2/SX2: -15872; SS2:
-7920) ○ ○ ○ ○ - - - R YES # D1004* Syntax check error code ○ ○ ○ ○ 0 0 - R NO 0 D1008* Step address when WDT is ON ○ ○ ○ ○ 0 - - R NO 0 D1009 Number of LV (Low voltage) signal ○ ○ ○ ○ - - - R YES 0