Siemens SIMATIC S7-200 System Manual page 145

Loading a New Current Value (Any Mode)
Changing the current value forces the counter to be disabled while the change is made. While the
counter is disabled, it does not count or generate interrupts.
The following steps describe how to change the counter current value of HSC1 (any mode):
1. Load SMB47 to write the desired current value:
SMB47 = 16#C0
2. Load SMD48 (double-word-sized value) with the desired current value (load with 0 to clear
it).
3. Execute the HSC instruction to cause the S7-200 to program HSC1.
Loading a New Preset Value (Any Mode)
The following steps describe how to change the preset value of HSC1 (any mode):
1. Load SMB47 to write the desired preset value:
SMB47 = 16#A0
2. Load SMD52 (double-word-sized value) with the desired preset value.
3. Execute the HSC instruction to cause the S7-200 to program HSC1.
Disabling a High-Speed Counter (Any Mode)
The following steps describe how to disable the HSC1 high-speed counter (any mode):
1. Load SMB47 to disable the counter:
SMB47 = 16#00
2. Execute the HSC instruction to disable the counter.
Enables the counter
Writes the new current value
Enables the counter
Writes the new preset value
Disables the counter
S7-200 Instruction Set Chapter 6
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