Serial Ports - Analog Devices ADSP-2106x SHARC User Manual

10 Serial Ports

When receive comparison is enabled, companding is disabled on the
transmitter and receiver. The MTCCSx register, which selects
multichannel companding when receive comparison is disabled,
determines whether the DSP performs a KEYWD comparison for the
enabled received channels. If the MTCCSx bit for a particlular channel
is '0,' the processor does not perform a comparison and always accepts
the receive data on that channel. If the MTCCSx bit for a particular
channel is '1,' the processor performs the comparison and accepts (or
rejects) the receive data, depending on the result of the comparison
and IMAT setting in the SRCTLx register.
The receive comparison feature lets the ADSP-21061's SPORTS
generate a DMA request or an interrupt when the received data
matches a specified condition on a specified channel in multichannel
mode. Without this feature, the SPORT would interrupt the processor
every time data was received and the processor would be required to
check if the data was meant for it or not. It is possible that most of the
time the data being sent is not meant for the processor. With the
receive comparison feature, the SPORT on a particular processor can
be programmed to interrupt only on messages meant for that
processor.
As a receive comparison example, consider four ADSP-21061s (A, B, C,
and D) which use SPORT0 (in multichannel mode) for interprocessor
communication. Channels 0, 1, 2, and 3 are used respectively by A, B,
C, and D to transmit control information between the processors.
Channels 4 through 10, 11 through 17, 18 through 24, and 25 through
31 are used respectively by A, B, C, and D to transmit data.
Because channels 0 through 3 are used to send control information
between the processors, the comparisons for incoming data is enabled
only for these channels. Initially, channels 4 through 31 may have
receive disabled. For this example, consider communication between
processors A and B only. The key word for comparison is
programmable; in this example, processor B can check for the key
word "START TRANSMIT TO B",
10 – 30
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