Rockwell Automation 1746-HSCE2 Multi-Channel High Speed Counter Module - Manual (Page 88)

Publication 1746-UM002B-EN-P - August 2004
5-6 Start Up, Operation, Troubleshooting, and Debug Mode
Output Does Not Turn Off
Check the associated module LED for the output.
If the LED is illuminated, check your program operation.
If the LED is not illuminated, check the wiring to your output device.
Check the leakage current of your connected device.
Soft Preset Does Not Work
Soft preset does not work when the counter’s P(n) bit is changed from
1 to 0 to 1 at the same time that the SP(n) bit is changed from 1 to 0 to
1. For example, when word 1 goes from 8003H to 0000H and back to
8003H, counter 1 is not preset.
Application Programming Errors Affecting Initialization
Typically, ladder logic manipulates 1746-HSCE2 parameters twice.
First, the ladder logic initializes the module at power-up using a
handshaking procedure shown in Application Examples 1, 2, and 3 in
Chapter 6. After initialization, ladder logic can be used to control the
1746-HSCE2 dynamically. For example, the program can manipulate
the module’s counter preset values (see Example 5 on page 6-18), or
the program can soft preset a module counter. The programmer must
be very careful to ensure that ladder logic programs intended to
manipulate module parameters after initialization do not affect the
initialization process.
A typical programming mistake is to use OTE instructions to set
1746-HSCE2 output image bits intended for post-initialization
operations (for example, soft presets). OTE instructions set or reset
the bit depending on whether the rung conditions are true or false.
For example, the following ladder rung sets the bit if the condition is
true, meaning bits B3/0 and B3/6 are set. However, it also clears the
bit if the rung condition is false, when either B3/0 or B3/6 is reset.
The result is that this logic, when scanned, manipulates the module’s
output image even if it was only intended to run after initialization
was complete.
Figure 5.2 OTE Instruction
Most programming errors are easy to locate, since the 1746-HSCE2
error bit (B3/1) is set and the configuration block pointer (N11:0)
points at the configuration block during which the error occurred.
However, errors that affect initialization are often very difficult to find
0001
B3:0
0
HSCE2_INIT_DONE
B3:0
6
SOFT_PRESET_TRGR HSCE2_CFG_BLK_1/1
O:1.1
1