Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 280)

Chapter 14
Using High-Speed Counter Instructions
14–30
Rung 2:1
This HSC instruction is not placed in the high–speed counter interrupt
subroutine. If this instruction were placed in the interrupt subroutine,
the high–speed counter could never be started or initialized (because an
interrupt must first occur in order to scan the high–speed counter
interrupt subroutine).
| High Speed Counter |
| +HSC––––––––––––––––––––+ |
|––––––––––––––––––––––––––––––––––––––+HIGH SPEED COUNTER +–(CU)–|
| |Type Encoder (Res,Hld)+–(CD) |
| |Counter C5:0+–(DN) |
| |High Preset 1250| |
| |Accum 1| |
| +–––––––––––––––––––––––+ |
Rung 2:2
This rung forces a high–speed counter low preset interrupt to occur each
RRUN mode entry. An interrupt can only occur on the transition of the
high–speed counter accum to a preset value (accum reset to 1, then 0).
This is done to allow the high–speed counter interrupt subroutine
sequencers to initialize. The order of high–speed counter initialization
is: (1)load high–speed counter parameters (2)execute HSL instruction
(3)execute true HSC instruction (4)(optional) force high–speed counter
interrupt to occur.
| 1’st High Speed Counter |
| Pass |
| S:1 +RAC––––––––––––––––––+ |
|––––] [––––––––––––––––––––––––––––––––––+–+RESET TO ACCUM VALUE +–+–|
| 15 | |Counter C5:0| | |
| | |Source 1| | |
| | | | | |
| | +–––––––––––––––––––––+ | |
| | High Speed | |
| | Counter | |
| | C5:0 | |
| +–––(RES)–––––––––––––––––+ |