The RMCM bit of MCR1 determines
whether all channels or only selected channels are enabled for reception. When RMCM
= 0, all 128 receive channels are enabled and cannot be disabled. When RMCM = 1, the
receive multichannel selection mode is enabled. In this mode:
- Channels can be individually
enabled or disabled. The only channels enabled are those selected in the
appropriate receive channel enable registers (RCERs). The way channels are
assigned to the RCERs depends on the number of receive channel partitions (2 or
8), as defined by the RMCME bit of MCR1.
- If a receive channel is disabled,
any bits received in that channel are passed only as far as the receive buffer
registers (RBRs). The receiver does not copy the content of the RBRs to the
DRRs, and as a result, does not set the receiver ready bit (RRDY). Therefore, no
DMA synchronization event (REVT) is generated and, if the receiver interrupt
mode depends on RRDY (RINTM = 00b), no interrupt is generated.
As an example of how the McBSP behaves
in the receive multichannel selection mode, suppose you enable only channels 0, 15,
and 39 and that the frame length is 40. The McBSP:
- Accepts bits shifted in from the
DR pin in channel 0
- Ignores bits received in channels
1-14
- Accepts bits shifted in from the
DR pin in channel 15
- Ignores bits received in channels
16-38
- Accepts bits shifted in from the
DR pin in channel 39