Sundance SMT148 - Manual (Page 21)

Version 1.4 Page 21 of 35 SMT148 User Manual
Input node (source)
The input node is defined as being an input to the switch fabric. It runs on the FPGA
system clock and has the following input and output signals.
WE input Write enable
HOLD output Receiver is full or already busy with another node, hold transfer
DATA input 8-bit data bus
Table 15: Input node IO
Note that all transfers are made in burst of 4 words. Therefore the HOLD flag should
be taken into account when the burst is completed.
Output node (destination)
The output node is an output from the switch fabric. It runs on the FPGA system
clock and has the following input and output signals.
WE output Write enable
FULL input Receiver full, transmitter must hold transfer
DATA output 8-bit data bus
DONE input Transfer completed
Table 16 : Output node IO
The output node interface, depending on the settings and data it received, and
detecting that the transfer is completed will assert a completion signal (DONE) to the
switch fabric that will disable the connection between the two nodes.
ComPorts (x8)
The ComPorts interfaces are directly connected to the switch fabric and allow
communication with external devices and modules using the ComPort or SDL
protocol (please refer to the
SDL Technical Specifications for more details). On the
switch fabric side the ComPorts must comply with the input and output node
descriptions.
Source
As an input to the switch fabric the ComPort interface can access any output
resources (destinations) connected to the switch fabric. To enable the connection to
a specific destination the ComPort interface must send the right address to the switch
fabric and once connected can start streaming data and/or control to the output node.
The ComPort source to the switch fabric also expects one 32-bit word before it can
start sending data to the switch fabric:
Bit 31: never ending transfer if 1. This setting can be useful when the connection
needs to always be enabled such as the DSP is streaming data to the DAC via the
ComPort without stopping. This bit must be set to 0 if the ComPort needs to be
dynamically reconnected to another node at some stage.
Bit 23 down to 0: transfer length. This is the total number of 32-bit words that will be
sent to the ComPort interface (excluding this word). This gives a maximum transfer
length of 2^26-4 bytes (64Mbytes). When the ComPort interface has received all data
it expected, it will go in an idle state for 2us before starting a new transfer if instructed
to do so. This setting is ignored if bit 31 is set to 1.