Changing Element Selection; End-Of-Subframe Interrupt; Enhanced Multichannel Selection Mode (C64X And C645X Dsps Only); Xmcm = 11B, Rpablk = 00B, Xpablk = X, Rcer = 1010B, Xcer = 1000B For Xmcm Operation - Texas Instruments TMS320C6000 DSP Reference Manual

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Figure 8-5. XMCM = 11b, RPABLK = 00b, XPABLK = X, RCER = 1010b, XCER = 1000b for XMCM Operation
FS(R/X)
DR
RRDY
RBR-to-DRR copy
DX
XRDY
DXR-to-XSR copy
8.3

Changing Element Selection

Using the multichannel selection feature, a static group of 32 elements can be enabled and remains
enabled with no CPU intervention until this allocation is modified. An arbitrary number of, group of, or all of
the elements within a frame can be accessed by updating the block allocation registers during the course
of the frame in response to the end-of-subframe interrupts (see
Note: Do not affect the currently selected subframe when changing the selection.
The currently selected subframe is readable through the RCBLK and XCBLK bits in MCR for receive and
transmit, respectively. The associated channel enable register cannot be modified if it is selected by the
appropriate (R/X)P[A/B]BLK register to point toward the current subframe. Similarly, the (R/X)PABLK and
(R/X)PBBLK bits in MCR cannot be modified while pointing to or being changed to point to the currently
selected subframe. If the total number of elements is 16 or less, the current partition is always pointed to.
In this case, only a reset of the serial port can change the element enabling.
8.4

End-of-Subframe Interrupt

At the end of every subframe (16 elements or less) boundary during multichannel operation, the receive
interrupt (RINT), if RINTM = 01b in SPCR, or transmit interrupt (XINT), if XINTM = 01b in SPCR, is
generated to the CPU. This interrupt indicates that a new partition has been crossed. You can then check
the current partition and change the selection of subframes in the A and/or B partitions if they do not point
to the current subframe. These interrupts are two CPU-clock high pulses. If RINTM = XINTM = 01b when
(R/X)MCM = 0 (non-multichannel operation), interrupts are not generated.
8.5

Enhanced Multichannel Selection Mode (C64x and C645x DSPs only)

In addition to the normal multichannel selection mode , the C64x and C645x McBSP has the enhanced
multichannel selection mode that allows up to 128 channels to be enabled at any given time. The
enhanced multichannel selection mode is selected by setting the enhanced receive multichannel selection
SPRU580E – December 2005
Read of DRR
(E3)
(E3)
Write of DXR
(E3)
(E1)
E1
Read of DRR
(E1)
RBR-to-DRR copy
(E1)
DXR-to-XSR copy
(E3)
Section 8.4).
Multichannel Selection Operation

Changing Element Selection

E3
RBR-to-DRR copy
(E3)
E3
65