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Appendix F
DMA Programming Examples
/* The following write causes any block transfer to the MXIbus
from either DMA controller to be a synchronous burst transfer by
setting both DMAxMBS bits in the SMCR. You can modify this write
so that both DMA controllers perform normal MXIbus block
transfers, or you can have one DMA controller perform normal
MXIbus block transfers and the other perform synchronous burst
transfers. Remember that MXIbus synchronous burst transfers cannot
be used when both the source and destination are located on the
MXIbus. */
write(A24, A24BASE + SMCR, BYTE, 0x38);
/* The following write is required to initialize the CHCRx for the
DMA controller that will be used. If you will be using both DMA
controllers, perform this write to both CHCR1 and CHCR2. */
write(A24, A24BASE + CHCR1, LONGWORD, 0x00004000);
/************************************************************
*
*
* Operation Setup:
This section sets up one of the DMA
*
* controllers to perform a data transfer from the VMEbus
*
* to the MXIbus and starts the operation. Repeat this
*
* process for each DMA operation. You can also perform
*
* these steps to the other DMA controller to start
*
* another operation without waiting for the first one to
*
* complete.
*
*
*
************************************************************/
/* The following write sets up the DMA Source Configuration
Register. It indicates that the source is located on the VMEbus
and that 32-bit block transfers with the address modifier code
0x3B will be used to access it. Table F-1, at the end of this
appendix, describes the address modifier codes that can be written
to this register. Remember that if the source is DRAM onboard the
VME-MXI-2, the address modifier code should be written with 0.
This step can be skipped if SCR1 was already written with the same
value from a previous DMA operation. This is useful if you will be
performing several DMA operations where the source device remains
constant. */
write(A24, A24BASE + SCR1, LONGWORD, 0x00E047BB);
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VME-MXI-2 User Manual