IP482 Industrial I/O Pack User’s Manual Counter Timer Module
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Acromag, Inc. Tel:248-295-0310 Fax:248-624-9234 Email:solutions@acromag.com http://www.acromag.com
33
Bit(s)
FUNCTION
2,1,0
Specifies the Counter Mode:
110
Period Measurement
3
Output Polarity (Output Pin ACTIVE Level):
0
Active LOW (Default)
1
1
Active HIGH
5, 4
InA Polarity / Signal Measured
00
Disabled (Default)
01
Active LOW portion of the signal starts period
measurement.
10
Active HIGH portion of the signal starts period
measurement.
11
Disabled
7, 6
InB Polarity / External Clock Input
00
Disabled (Default)
01
External Clock Enabled
10
External Clock Enabled
11
Disabled
9,8
InC Polarity / External Trigger
00
Disabled (Default)
01
Active LOW Trigger
10
Active HIGH Trigger
11
Disabled
12,11,10
Clock Source
Carrier Operational Freq.
8MHz
32MHz
000
Internal @ (Default)
0.5MHz
2MHz
001
Internal @
1MHz
4MHz
010
Internal @
2MHz
8MHz
011
Internal @
4MHz
16MHz
100
Internal @
8MHz
32MHz
101
External Clock
Up to 2MHz
Up to 8MHz
13
Input Debounce Enable
0
Disabled (Default)
– No Debounce Applied to any
Input.
1
Enabled
– Reject Source or Trigger Pulses (noise)
less than or equal to 2.5
s.
Using Debounce will add
an error of up to 800ns when used for period
measurement.
14
Not Used (bit reads back as 0)
15
Interrupt Enable
0
Disable Interrupt Service (Default)
1
Enable Interrupt Service
COUNTER CONTROL
REGISTER
INPUT PERIOD
MEASUREMENT
Table 3.16:
Counter Control
Register
(Input Period Measurement)
1. The default state of the
output pin is high (output has
pullup installed). Bit 3
specifies the active output
polarity when the output is
driven.
2. The available clock sources
are determined by the
operational frequency of the
carrier board. For an 8MHz
carrier, bit 0 of the Board
Control Register located at the
base address plus an offset of
0H must be set low. For a
32MHz carrier, the bit must be
set high.