cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 52

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

2.1
The SIU is the module that logically connects the 32 serial ports (line interface unit) with serial line processing by
performing the serial-to-parallel conversion for the receive side, and parallel to serial for the transmit side. The SIU
contains two main blocks, RSIU for the receive path and TSIU for the transmit path. The RSIU main function is
multiplexing 32 serial ports into one logical port for the receive serial line processing block. The TSIU main function
is demultiplexing one logical port from the transmit serial line processing block to 32 serial ports.
The SIU main functions:
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TSIU (Transmit Serial Interface Unit) is responsible for informing TSLP (Transmit Serial Line Processor) when it is
time to perform a transmit channel poll by counting a programmable (TPOLLTH) number of frames. For the TSBUS
mode, one frame is defined as the STB strobe interval. TSIU is also responsible for requesting transmit data from
TSLP for each transmitted time slot (i.e., for each VSP).
As for the RSIU, when data comes through the serial ports, it is stored in local buffers. At this stage, all line signals
are synchronized to the system clock, or the PCI bus rate (either 33 MHz or 66 MHz). At each cycle, the RSIU
transfers a byte received from one of the 32 ports to the Receive Serial Line Processor (RSLP). For the port being
served, the RSIU translates the time slot to a channel number (using an internal map) and provides certain
parameters that are needed by the RSLP to process the incoming data. Similar to the TSIU, for the TSBUS mode,
one frame is defined as the STB strobe interval.
28500-DSH-002-C
Multiplexing/demultiplexing 32 serial ports to one port for the receive path, and one port to 32 serial ports for
the transmit path, respectively.
Performs frame integrity check while operating in channelized mode. SIU verifies the length of incoming/
outgoing frames according to the configured number of time slots. In case of error a Change Of Frame
Alignment (COFA) is reported (see COFA description both modes convention and TSBUS mode).
Translates the time slot to logical channel number using the configured receive and transmit time slot map.
Provides a poll indication per port, see RPOLLTH or TPOLLTH bit fields in RSIU Port Configuration register
and TSIU Port Configuration register, which counts the frames of the poll interval of 1, 2, 4, 8, 16, 64, 128, or
256 frame interval.
Generates the following interrupts:
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RxOOF, where ROOF signal is asserted
RxFREC, where ROOF signal is deasserted
RxCOFA, where RSYNC signal is asserted in an unexpected place
RxCREC, where COFA condition is off for the receive port
TxCOFA, where TSYNC signal is asserted in an unexpected place
TxCREC, where COFA condition is off for the transmit port
Serial Interface Unit (SIU)
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Internal Architecture
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