MDS213 Datasheet, PDF (39/120 Pages) Zarlink Semiconductor Inc – 12-Port 10/100Mbps + 1Gbps Ethernet Switch

MDS213
Data Sheet
The XPipe interface employs 32 data signals and three control signals for each direction. The pin connections
between two MDS213 devices are depicted in Figure 8. These 32 data signals form a 32-bit-wide transmission data
pipe that carries XpressFlow messages to and from the devices. The direction of all signals are from the source to
the target device, except for the flow control signal, which sends messages in the opposite direction; from the target
to the source. The three control signals consist of: a Transmit Clock signal, a Transmit Data Enable signal, and a
Flow Control signal.
The Transmit Clock signal (X_DCLKO), provides a synchronous clock to sample the data signals at the target
device. The source device provides the Transmit Data Enable signal (X_DENO) that envelops an entire XPipe
message (including the Header and the Payload) and is used to identify the message boundary from the received
data stream. The timing relationship between the data, clock, and data enable signals are described in the XPipe
Timing (Section 10.2).
The Flow Control signal (X_FC) monitors the state of the receiving queue at the target end to prevent XPipe
message loss. When the target end does not have enough space to accommodate an entire XPipe message, the
target device sends a XOFF signal by driving the X_FCO signal to LOW. The source device will stop further
transmission until the X_FCI signal asserts the XON state, which is an active HIGH (Refer to Table 4).
Signal Name
Source End
Target End
X_DO[31:0]
X_DI[31:0]
X_DCLKO
X_DCLKI
X_DENO
X_DENI
X_FCI
X_FCO
Description
32-bit-wide Transmit Data Bus - Includes a XPipe Message
Header and follows by the data payload
Transmit Clock - Synchronous data clock provided by the source
end
Transmit Data Enable - Provided by the source end to envelop
the entire XPipe message
Flow Control Signal- A flow control pin from the target end to
signal the source end to active XON/XOFF.
Table 4 - Summary Description of the Source and Target End Signals
The XPipe Message Header provides the payload size, type of message, routing information, and control
information for the XPipe incoming message. The routing information includes the device ID and port ID. The
header size is dependent upon the message types and may be 2 to 4 words in length.
2-4 Words Header
XpipeFlow Message
Header
0-64 Words Payload
Data Payload
Figure 9 - XPipe Message Header
8.2 XPipe Timing
The source device generates the X_CLKO signal to provide a synchronous transmit data clock. The Receiver will
then sample the data on the falling (negative) edge of the clock, as shown in Figure 10.
To identify the boundary between the XPipe messages and the data stream, the source device uses the X_DENO
signal to envelop the entire XPipe message. That is, a rising (positive) edge at the beginning of the first double word
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