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Offset | Register | Parameter Description | Value (dec) | Value (hex) |
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22 | 122 | Channel description 5: |
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| Seg. Sel. : Length | 8 | 0008 |
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23 | 123 | Offset | 0 | 0000 |
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24 | 124 | Channel description 6: |
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| Seg. Sel. : Length | FF07 | |
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25 | 125 | Offset | 0 | 0000 |
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The following is a description of the above control block.
∙The status register is telling us that the FBK is in the Active state (2 - Active state). This means the function block is executing normally, and taking a sample each time the function block is encountered in program logic. The extra status data tells us that we have already taken more that 512 samples, and thus the sample buffer has already wrapped at least once.
∙The event recorder is configured to trigger based on the Trigger boolean input.
∙The reserved parameters are always set to 0.
∙The user selected 24 channels of data with a sample buffer size of 512 samples. The sample buffer is not 512 bytes! It is 512 x (24/8) = 1536 bytes or 768 words.
∙The number of samples that are to be gathered after the trigger is 12. (each sample is 3 bytes long)
∙We are to scan the input module in rack 0 slot 4 so its current values are available for sampling.
∙The data segment is 0x08 (registers) and the offset is 200 which places the start of the data block at %R0201. The offset is a
∙The next section contains the channel descriptions. In this example 6 channel descriptions have been defined.
1.The first channel description selects the %I Segment with a Length of 1, and offset of 0. This chooses %I0001 for channel 1.
2.The second channel description selects the NULL Selector with Length of 3, and offset of 0. The NULL selector causes channels 2 - 4 to be ignored or “skipped”. These channels will always contain a sample value of Zero.
3.The third channel description selects the Input Module Selector with a length of 3, and offset of 12. The Input Module Selector causes samples to be taken from the input module. This channel description chooses the values in points 13, 14, and 15 of the input module for channels 5 - 7.
4.The fourth channel description selects the %Q Segment with a Length of 2, and offset of 8. This chooses %Q0009 and %Q0010 for channels 8 and 9.
5.The fifth channel description is another Input Module Selector. It has a length of 8, and offset of 0. This causes the values for points 1 to 8 of the input module to be placed in channels 10 - 17.
6.The sixth channel description is another NULL Selector. It has a Length of 7, and offset of 0. This NULL channel description causes channels 18 - 24 to be filled with Zeros. This
| Chapter 4 Series |
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