PCIe-24DSI32
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3-21
To invoke the scan-synchronized mode, set the SYNCHRONIZE SCAN control bit HIGH in the
BCR, and wait for the CHANNELS READY flag (3.4.4) in the BCR to undergo a LOW-to-HIGH
transition.
While the CHANNELS READY flag is LOW, the following sequence is executed by
the local controller:
1. The Group-0 sample clock (Section 3.6.1) is distributed to all input channels,
2. All ADC's are channel-synchronized (Section 3.6.2),
3. All channels are scan-synchronized.
The buffer clears to empty, and the first two scans are discarded to ensure full synchronization.
Subsequent samples are scan-synchronized as described above. The Channels-Ready flag
can be used to generate an interrupt at the end of the process.
Notice that all enabled input channels receive the sample clock selected for Group-0
while
operating in the scan-synchronized mode
, and the sample clock settings for Group-1 through
Group-3 are ignored. Disabled groups remain disabled.
Use the following sequence to scan-synchronize multiple boards (Paragraph 3.6.3)
Synchronize ADC's:
1. On all boards: Set SYNCHRONOUS SCAN;
Wait for Channels Ready LOW-to-HIGH on all boards (LOW 1-100ms).
(All ADC's are synchronized, but sample-skewed between boards)
2. On Initiator:
Set SOFTWARE SYNC;
Wait for Channels Ready LOW-to-HIGH on all boards (LOW 1-100ms).
(All ADC's are scan synchronized; but the data buffers are skewed)
Global Buffer Clear:
3. On all boards: Set the CLEAR BUFFER ON SYNC bit,
4. On Initiator: Set SOFTWARE SYNC;
Wait for Channels Ready LOW-to-HIGH on the initiator. (LOW 10us to 5ms),
(All ADC's and buffers are scan-synchronized)
5. On all boards: Clear the CLEAR BUFFER ON SYNC bit.
For optimum DC performance, execute autocalibration on all boards after synchronizing the
ADC's on all boards, and follow the procedure with a 'global clear' operation.
NOTE: If autocalibration is executed while scan-synchronized, repeat the global buffer
clear sequence (Steps 3 through 5).
To simplify this operation, the
CLEAR BUFFER ON SYNC control bit can be allowed to remain HIGH while scan-
synchronized.
