Chapter 1. Introduction
5
1.3.1
The Picoblaze Soft Microprocessor
Picoblaze is a soft microprocessor offered by Xilinx.
It is based on an 8-bit RISC
architecture and can reach speeds up to 100 MIPS on the Virtex 4 FPGA’s family. The
processor has an 8-bit address and data port for access to a wide range of peripherals.
The license of the cores allows their free use, albeit only on Xilinx devices, and they come
with development tools. The PicoBlaze microcontroller core is totally embedded within
the target FPGA and requires no external resources. The basic functionality is easily
extended and enhanced by connecting additional FPGA logic to the microcontroller’s
input and output ports. the PicoBlaze peripheral set can be customized to meet the
specific features, function, and cost requirements of the target application. Because the
PicoBlaze microcontroller is delivered as synthesizable VHDL source code, the core is
future-proof and can be migrated to future FPGA architectures, effectively eliminating
product obsolescence fears. Being integrated within the FPGA, the processor reduces
board space, design cost, and inventory[
1.3.2
The Microblaze Soft Microprocessor
MicroBlaze is a 32-bit RISC Harvard architecture soft processor core which is created
and offered for free by Xilinx. They key feature of this processor is its high customiz-
ability and flexibility. MicroBlaze contains over 70 user-configurable options, enabling
virtually any processor use case from a very small footprint state machine or micro-
controller to a high performance compute-intensive micrprocessor-based system running
Linux, operating in either 3-stage pipeline mode to optimize size, or 5-stage pipeline
mode to optimize speed. These parameters include an optional IEEE-754 compatible
single precision FPU, a hardware divider, a barrel shifter, data and instruction caches,
exception handling capabilities, hardware debug logic and many more[
]. Both Picoblaze
and Microblaze come freely with the Embedded Development Kit (EDK) which is of-
fered from Xilinx. Both of these processors are small and focus mainly in flexibility and
low power consumption.