Limit 1 (Index 0x08n0:13) and Limit 2 (Index 0x08n0:14), Swap Limit bits
Limit 1 (index 0x08n0:13) and Limit 2 (index 0x08n0:14)
Indices 0x08n0:07 and 0x08n0:08 are used to activate limit value monitoring.
If the limits of the values that can be entered in indices 0x08n0:13 and 0x80n0:14 are violated, the bits in the indices are set accordingly (see the table and the example below).
Channel | Index for Limit 1 | Index for Limit 2 |
---|---|---|
1 | 0x60p0:03 | 0x60p0:04 |
2 | 0x60p0:0C | 0x60p0:0D |
3 | 0x60p0:15 | 0x60p0:16 |
4 | 0x60p0:1E | 0x60p0:1F |
With p = 0 for Port1.... p = 3 for Port4
Limit output (2 bit):
0: Limit function not active
1: Value < limit value
2: Value > limit value
3: Value = limit value
Limit evaluation The limit evaluation assumes a signed representation. The conversion to the desired representation (index 0x80n0:02) only takes place after the limit evaluation. |
Example limit evaluation for EPI3174
Port1, channel 1; Limit 1 and Limit 2 enabled, Limit 1 = 2.8 V, Limit 2 = 7.4 V, representation: signed integer
Input in index 0x0800:13 (limit 1):
(2.8 V / 10 V) * 216 / 2-1 = 9,174dec
Input in index 0x0800:14 (limit 2):
(7.4 V / 10 V) * 216 / 2-1 = 24,247dec
Output:
Input channel 1 | Limit1 index 0x6000:03 | Limit2 index 0x6000:04 |
---|---|---|
1.8 V | 0x01hex, (Limit 1, limit value undershot) | 0x01hex, (Limit 2, limit value undershot) |
2.8 V | 0x03hex, (Limit 1, limit value reached) | 0x01hex, (Limit 2, limit value undershot) |
4.2 V | 0x02hex, (Limit 1, limit value exceeded) | 0x01hex, (Limit 2, limit value undershot) |
8.5 V | 0x02hex, (Limit 1, limit value exceeded) | 0x02hex, (Limit 2, limit value exceeded) |
Swap Limit Index 0x80n0:0E
The limit function can be inverted by SwapLimitBits in index 0x80n0:0E.
Output n (2 bits):
SwapLimitBits setting | Value |
---|---|
FALSE (default setting) |
|
TRUE |
|
Linking in the PLC with 2-bit values The limit information consists of 2 bits. Limitn can be linked to the PLC or a task in the System Manager: PLC: IEC61131-PLC contains no 2-bit data type that can be linked with this process data directly. In order to transmit the limit information, therefore, define an input byte, e.g. Link the limit to an existing variable. Additional task: 2-bit variables can be created in the System Manager. Linking of 2-bit variable to additional task |