15.5.7 Transmit Multichannel Selection Modes
The XMCM bits of XCR2 determine whether all channels or only selected channels are enabled and unmasked
for transmission. More details on enabling and masking are in
. The McBSP has three transmit
multichannel selection modes (XMCM = 01b, XMCM = 10b, and XMCM = 11b), which are described in the
following table.
Table 15-13. Selecting a Transmit Multichannel Selection Mode With the XMCM Bits
XMCM
Transmit Multichannel Selection Mode
00b
No transmit multichannel selection mode is on. All channels are enabled and unmasked. No channels can be
disabled or masked.
01b
All channels are disabled unless they are selected in the appropriate transmit channel enable registers
(XCERs). If enabled, a channel in this mode is also unmasked.
The XMCME bit of MCR2 determines whether 32 channels or 128 channels are selectable in XCERs.
10b
All channels are enabled, but they are masked unless they are selected in the appropriate transmit channel
enable registers (XCERs).
The XMCME bit of MCR2 determines whether 32 channels or 128 channels are selectable in XCERs.
11b
This mode is used for symmetric transmission and reception.
All channels are disabled for transmission unless they are enabled for reception in the appropriate receive
channel enable registers (RCERs). Once enabled, they are masked unless they are also selected in the
appropriate transmit channel enable registers (XCERs).
The XMCME bit of MCR2 determines whether 32 channels or 128 channels are selectable in RCERs and
XCERs.
As an example of how the McBSP behaves in a transmit multichannel selection mode, suppose that XMCM =
01b (all channels disabled unless individually enabled) and that you have enabled only channels 0, 15, and 39.
Suppose also that the frame length is 40. The McBSP:…
1. Shifts data to the DX pin in channel 0
2. Places the DX pin in the high impedance state in channels 1-14
3. Shifts data to the DX pin in channel 15
4. Places the DX pin in the high impedance state in channels 16-38
5. Shifts data to the DX pin in channel 39
Multichannel Buffered Serial Port (McBSP)
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
909
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Summary of Contents for TMS320 2806 Series
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