5Serial Ports
5 – 33
RFS
DR
TDV
DT
W0-3 W8-11 W16-19
SCLK
B3 B2 B1
B2
DR
RFS
B0 IGNORED B3
DT
B2B3 B0 B3 B2B1
TDV
WORD 0 WORD 1 WORD 2
frame signal inversion (INVRFS), companding (DTYPE) and
autobuffering are unchanged in the multichannel mode. Note: It is
important that RFS does not occur more than once per frame in
multichannel mode.
Instead of providing frame synchronization, the TFS0 signal functions as a
transmit data valid (TDV) signal in multichannel mode. TDV is asserted
while the transmitter is active. TDV can be active high or low, and its
polarity is controlled by the INVTFS bit, renamed INVTDV in this context.
If INVTDV is a 1, TDV is active low; otherwise it is active high. TDV can
be used to enable additional buffer logic, if required.
Figure 5.28 shows the start of a multichannel transfer. As in earlier
examples, word length is four bits (SLEN=3) and frame sync signals are
active high. Multichannel frame delay (MFD) is one SCLK cycle. For the
purpose of illustration, words 0 and 2 are selected for receiving and words
1 and 2 are selected for transmission.
Figure 5.28 Start Of Multichannel Transfer
Figure 5.29 shows a complete 24-word block in the multichannel mode,
with complete words represented in the waveforms instead of individual
bits. Receiving is active for all words and transmitting is active for words
0–3, 8–11 and 16–19 only.
Note: The ADSP-2105 has only one serial port (SPORT1) and does not
support multichannel operation.
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