DS80C390_00 Datasheet, PDF (143/155 Pages) Dallas Semiconductor – High-Speed Microcontroller User’s Guide Supplement

DS80C390 High-Speed Microcontroller User’s Guide Supplement
Case 2)
Software-Initiated Reply (Using TIH as Gating Control)
CAN module wishes to receive an RFR and wait for software to determine when and what
will be transmitted in reference to RFR.
1. Software sets T/ R = 1, MSRDY = 0, DTUP = 0, and TIH = 1.
2. Software then loads data into respective message center.
3. Software sets MSRDY = 1, DTUP = 1 and TIH = 1 in same instruction.
Note: Software does not change MTRQ = 0 from previous completed transmission
4. CAN does not transmit data (MTRQ = 0), but waits for RFR.
5. CAN successfully receives RFR.
6. CAN forces MTRQ = 1 and EXTRQ = 1.
7. CAN loads DTBYC from RFR and ID into arbitration registers.
8. CAN waits for software to read message center and determine the fact that EXTRQ = 1.
9. Software may load data into message center (or it may already have the data established).
10. Software writes MSRDY = 1, DTUP = 1 and TIH = 0 in same instruction.
11. CAN will automatically transmit data (as per RFR DTBYC) in respective message center.
12. CAN clears EXTRQ = 0 and MTRQ = 0.
Case 3)
Software-Initiated Reply (Reply via same message center, using TIH as Gating Control)
CAN module wishes to receive an RFR in a receive-configured (T/ R = 0) message
center. When the data is received, the message center will be reconfigured send data back
to the remote request node. This relationship is not possible for message center 15.
1. Software sets T/ R = 0, MSRDY = 1, and DTUP = 0 and awaits either data frame or RFR.
Note: Software does not change MTRQ = 0 from previous completed transmission
2. CAN successfully receives RFR.
3. CAN forces EXTRQ = 1 and DTUP = 1.
4. MTRQ can not be written to a 1 by the CAN when T/ R = 0 and is left as MTRQ = 0
5. CAN loads DTBYC from RFR and ID into arbitration registers.
6. CAN waits for Software to read message center and determine the fact that EXTRQ = 1.
7. Software disables message center and converts message center into transmit message center.
8. Software clears MSRDY = 0 to disable message center. Software leaves EXTRQ = 1.
9. Software then forces message center to transmit mode, T/R = 1.
10. Software writes MSRDY = 0, DTUP = 0 and TIH = 1 in preparation to load data.
11. Software loads data into message center.
12. Software writes MSRDY = 1, MTRQ = 1, DTUP = 1 and TIH = 0 in same instruction.
13. Note that Software leaves EXTRQ = 1.
14. CAN will automatically transmit data (as per RFR DTBYC) in respective message center.
15. CAN clears EXTRQ = 0 and MTRQ =0.
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