I/O modules • 113
Counter modules 750-404/000-003
Modular I/O System
ETHERNET TCP/IP
Structure of the Input and Output data
The input data represents the CLOCK frequency as a binary value. The repre-
sentation depends on the RANGE_SEL bits in the CONTROL byte. Even the
method of measuring is selected via these bits. The following table illustrates
the different modes.
RANGE_S
EL1
RANGE_S
EL0
Method of measurement
Representation of measuring value
0
0
Integration over 1 Period
Frequency in
1
/
1000
Hz
0
1
Integration over 4 Periods
Frequency in
1
/
100
Hz
1
0
Integration over 16 Periods
Frequency in
1
/
10
Hz
1
1
Integration over 16 Periods
Frequency in Hz
Attention
When a new frequency range is requested, the application has to wait for valid
data until the RANGE_SEL ACK bits contain the new frequency range. The
maximum delay can be calculated using the following formula.
Number of periods to be integrated
actual frequency
If the gate is enabled the input data contains the last valid frequency value. In
this state the application cannot request a new range.
The valid frequency range stretches from 0.1 Hz (100
D
) up to 10 kHz
(100000
D
).
To recognize static CLOCK signals, a watchdog timer is implemented. The de-
fault value for the timer is 10s. The timer resets on every Power On.
The application is able to change the watchdog time during operation by using
the CONTROL byte.
This can be initiated by writing the corresponding value into the output bytes
OUTPUT_DATA 1 and OUTPUT_DATA 0 before setting the T
VD
REQ bit in
the CONTROL byte.
The success of the parameter transfer is acknowledged by the module via the
T
VD
ACK bit in the STATUS information.
Attention
The range of the watchdog timer stretches from 0 to 16383ms (0x0000
H
to
0x3FFF
H
) in steps of 1ms per digit.
Values which raise the permitted range of the watchdog timer are masked with
0x3FFF.
If the maximum possible frequency of the different ranges is raised (see the
table with maximum frequency ratings), the module will return the non valid
data 0xFFFFFFFF
H
.
T
Dmax
= 2 •