Processor Local Bus Functional Model Toolkit User's Manual

Chapter 3. PLB Toolkit Test Bench
Figure 3 shows the default configuration of the PLB toolkit test bench environment. It contains
instantiations of a PLB master model, PLB slave model, PLB core, and a PLB monitor model. It also
contains the distributed multiplexers and logic to implement the PLB bus using AND/OR HDL
statements.
Note: Default configuration instantiates four masters and four slaves. The current PLB
implementation supports up to eight masters.
Designs under test may be instantiated in the toolkit test bench HDL which replace the default
configuration. Also, the bus functional models may be instantiated in other test bench environments
which include designs under test.
PLB
Monitor
PLB
Master 0
Model
PLB
Slave 0
Model
PLB
Master 1
Model
Processor Local Bus Core
PLB
Slave 1
Model
PLB
Master 2
Model
PLB
Slave 2
Model
PLB
Master 3
Model
PLB
Slave 3
Model
Figure 3. PLB Toolkit Testbench(plb_complex.vhd/.v)
3.1 Programmable PLB Data Bus Width and Automatic Replication
The PLB toolkit test bench uses a constant called PLB_DATA_BUS_WIDTH in declaring the actual
PLB arbiter data bus signals. This constant defaults to 128 for the PLB 4.x toolkit, but may be
changed to be 64 or 32 for other PLB arbiter implementations. The toolkit will automatically scale the
model I/O’s and bus operations based on the PLB_DATA_BUS_WIDTH constant.
In addition to programmable arbiter data bus widths, the PLB Test Bench contains logic to
automatically perform the necessary Byte Enable(BE) and Data Bus replication as described by the
PLB 4.x Bus Architecture specification. This replication is performed when necessary as smaller PLB
masters and Slaves are connected to a wider data path PLB Arbiter. The master BE’s and write data
bus(wrDbus) are replicated to the arbiter, and the slave read data bus(rdDbus) is also replicated to
the arbiter when necessary. The test bench uses the msize/ssize signals from the masters and slave,
together with other bus control signals to automatically generate a “mirror” signal.
Version 4.9.2 PLB Toolkit Test Bench 9