Embedded Software for SoC - Grupo de Mecatrônica EESC/USP

Analysis of HW/SW On-Chip Communication in MP SOC Design 131
since simultaneous accesses to the physical buffer are possible. For instance,
if the physical buffer size is 2, two communication transactions with data
size of one can use the same physical buffer. The number of communication
transactions is not limited unless the buffer is full. In terms of physical buffer
implementation, we assume the number of memory ports of physical buffer
as the maximum number of simultaneous accesses to the physical buffer. Our
future work includes ILP formulation for the case where the number of
memory ports of physical buffer is less than the maximum number of
simultaneous accesses to the physical buffer.
For the ILP formulation of this constraint, we use a Boolean variable
is 1 if the physical buffer is used by a communication node
and 0 otherwise. In our physical buffer model, we assume for safety that the
data is pushed to a buffer at the start time of write operation and popped at
the finish time of read operation. Thus, if the access type of a node is read,
the value of is determined as follows:
or if the access type of a communication node
is write,
However, since is a non-linear function of another variable
or it cannot be a variable in the ILP formulation as it is. To resolve
this, the condition for is formulated as follows (for the case of write
access type):
where TimeMax is a big integer constant and is a dummy variable. If time
the right hand side of the equation is negative. For the left hand
side of the equation to be negative, is 0 because is equal to or smaller
than TimeMax. If
the right hand side is zero or positive.
should be 1 because is bigger than 1.
The physical buffer contention constraints are modeled as follows.
for all physical buffer
for all communication notes
using
where is a communication node using n is the number of communication
nodes that use physical buffer
is the maximum size of
physical buffer and is the data size of communication node