Transmit Multichannel Selection Mode
Multichannel Selection Modes
5-12
SPRU592E
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
5.7.1 Disabling/Enabling Versus Masking/Unmasking
For transmission, a channel can be:
-
Enabled and unmasked (transmission can begin and can be completed)
-
Enabled but masked (transmission can begin but cannot be completed)
-
Disabled (transmission cannot occur)
The following definitions explain the channel control options:
Enabled channel
A channel that can begin transmission by passing
data from the data transmit register(s) (DXR(s)) to
the transmit shift registers (XSR(s)).
Masked channel
A channel that cannot complete transmission. The
DX pin is held in the high-impedance state; data
cannot be shifted out on the DX pin.
In systems where symmetric transmit and receive
provides software benefits, this feature allows
transmit channels to be disabled on a shared serial
bus. A similar feature is not needed for reception
because multiple receptions cannot cause serial bus
contention.
Содержание TMS320VC5509
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