4-8 Input / Output MN1902
4.3.4 Special functions on DIN4 and DIN5 - fast inputs
Flex+Drive
II
only:
DIN4 and DIN5 can be configured using the FASTSELECT keyword to perform special
functions:
H Fast interrupt hardware position capture input. The position of the axis is captured in real
time and can be read using the Mint keyword FASTPOS.
H Master or auxiliary encoder input capture, read using the Mint keyword
FASTAUXENCODER
(DIN5 only).
The maximum latency to read the fast position is approximately 1µs. The fast interrupt will be
latched on a pulse width of about 30µs, although a width of 100µs is recommended to ensure
capture. To prevent subsequent inputs causing the captured value to be overwritten, the
interrupt is latched in software. It is necessary to clear the latch before subsequent interrupts
can be detected. See the Mint help file. Both inputs are fitted with Schmitt trigger devices.
Note: The fast inputs are particularly sensitive to noise, so inputs must use shielded
twisted pair cable. The inputs are not opto-isolated.
Do not connect mechanical switches, relay contacts or other sources liable to
signal ‘bounce’ directly to the fast inputs. This could cause unwanted multiple
triggering.
Active high: DINx=+24VDC (±20%)
CREF=0V
CREF
Pin 7
DINx
Pins 14-15
4k7
33pF
HCPL2231
to CPU
Vcc
FlexDrive
II
Active low: DINx=0V
CREF=+24VDC (±20%)
1k
10k
DGND
Figure 27 - X3 pulse a nd direction / fast digit al input circuit
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