cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 35

• Manufacturer Part Number: cx28500
• Description: Cx28500 Multichannel Synchronous Communications Controller
• Manufacturer: Mindspeed Technologies

Introduction
TxSIU when it is ready for transmission. The request, in terms of a channel number, is passed to the TSLP. If the
TSLP has data for the requested channel, then it will give that data to the TxSIU. Otherwise, it will generate a
request, also a channel number, to the TxDMA. The TxDMA serves the channel based on its FIFO fill-state and its
data availability. A channel is queued in TxDMA Service Request Queue when the channel FIFO contains less than
the threshold value, or at least 32 empty dwords for the channel.
When a channel request gets to the top of the TxDMA Service Requests Queue, the TxDMA will serve this channel
until the channel FIFO is full. Since this may involve more than one PCI transaction, the channel is inserted at the
end of the TxDMA Service Request Queue after each transaction. The TxDMA gets data from shared memory on
a per-channel basis when the internal FIFO is not full. If TxDMA has either enough data or a complete HDLC
message, then it will start transferring data to the TSLP. The TSLP, in turn, does the necessary formatting, if any,
and sends the data to the TxSIU for transmission. The SIU uses a fixed priority scheme where port A has priority
over port B (when A is smaller than B). For the selected port, the SIU uses a internal map conversion to identify
which channel number data is transferred.
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