Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 267)

Chapter 14
Using High-Speed Counter Instructions
14–17
Parameter
Image
Location
Up Counter
Only
Bidirectional
Counters
Description
N5 Output Mask Output Mask
Identifies which group of four bits in the output file
(word 0) are controlled.
000F=bits 3–0
00F0=bits 7–4
0003=bits 0 and 1
00FF= bits 7–0
N6
Output
Source Output High
Source (Up count) The status of bits in this word are
written “through” the mask to the actual outputs.
N7 High Preset High Preset
(Up count) When the accumulator reaches this
value, the output source is written through the
output mask to the actual outputs and the HSC
subroutine (file 4) is scanned.
N8 Reserved
Output Low
Source (Down count) The status of bits in this word are
written “through” the mask to the actual outputs.
N9 Reserved Low Preset
(Down count) When the accumulator reaches
this value, the output source is written through
the output mask to the actual outputs and the
HSC subroutine (file 4) is scanned.
The bits in the output mask directly correspond to the physical outputs. If a
bit is set to 1, the corresponding output can be changed by the high-speed
counter. If a bit is set to 0, the corresponding output cannot be changed by
the high-speed counter.
The bits in the high and low sources also directly correspond to the physical
outputs. The high source is applied when the high preset is reached. The
low source is applied when the low preset is reached. The final output states
are determined by applying the output source over the mask and updating
only the unmasked outputs (those with a 1 in the mask bit pattern).
You can always change the state of the outputs via the user program or
programming device regardless of the output mask. The high-speed counter
only modifies selected outputs and output image bits based on source and
mask bit patterns when the presets are reached. The last device that changes
the output image (i.e., user program or high-speed counter) determines the
actual output pattern.
!
ATTENTION: Forces override any output control from either
the high-speed counter or from the output image. Forces may
also be applied to the high-speed counter inputs. Forced inputs
are recognized by the high-speed counter (e.g. a forced count
input off and on increments the high-speed accumulator).
The high-speed counter hardware is updated immediately when the HSL
instruction is executed regardless of high-speed counter type (Up Counter or
Bidirectional Counter). For the Up Counters, the last two registers are
ignored since the low preset does not apply.