<s>
PicoBlaze	B-Device
is	O
the	O
designation	O
of	O
a	O
series	O
of	O
three	O
free	O
soft	B-Device
processor	I-Device
cores	O
from	O
Xilinx	O
for	O
use	O
in	O
their	O
FPGA	B-Architecture
and	O
CPLD	B-General_Concept
products	O
.	O
</s>
<s>
They	O
are	O
based	O
on	O
an	O
8-bit	O
RISC	B-Architecture
architecture	O
and	O
can	O
reach	O
speeds	O
up	O
to	O
100	O
MIPS	O
on	O
the	O
Virtex	O
4	O
FPGA	B-Architecture
's	O
family	O
.	O
</s>
<s>
The	O
processors	B-General_Concept
have	O
an	O
8-bit	O
address	O
and	O
data	O
port	O
for	O
access	O
to	O
a	O
wide	O
range	O
of	O
peripherals	O
.	O
</s>
<s>
The	O
license	O
of	O
the	O
cores	O
allows	O
their	O
free	O
use	O
,	O
albeit	O
only	O
on	O
Xilinx	O
devices	O
,	O
and	O
they	O
come	O
with	O
development	B-Application
tools	I-Application
.	O
</s>
<s>
Also	O
PacoBlaze	O
,	O
a	O
behavioral	O
and	O
device	O
independent	O
implementation	O
of	O
the	O
cores	O
exists	O
and	O
is	O
released	O
under	O
the	O
BSD	B-Operating_System
License	I-Operating_System
.	O
</s>
<s>
The	O
PauloBlaze	O
is	O
an	O
open	O
source	O
VHDL	B-Language
implementation	O
under	O
the	O
Apache	B-Application
License	I-Application
.	O
</s>
<s>
The	O
PicoBlaze	B-Device
design	O
was	O
originally	O
named	O
KCPSM	O
which	O
stands	O
for	O
"	O
Constant(K )	O
Coded	O
Programmable	O
State	O
Machine	O
"	O
(	O
formerly	O
"	O
Ken	O
Chapman	O
's	O
PSM	O
"	O
)	O
.	O
</s>
<s>
When	O
instantiating	O
a	O
PicoBlaze	B-Device
microcontroller	O
in	O
VHDL	B-Language
,	O
the	O
respective	O
KCPSM	O
component	O
name	O
must	O
be	O
used	O
.	O
</s>
<s>
As	O
a	O
resource	O
optimization	O
,	O
it	O
is	O
possible	O
for	O
two	O
PicoBlaze	B-Device
cores	O
to	O
share	O
the	O
same	O
1k	O
x	O
18	O
instruction	O
PROM	O
,	O
taking	O
advantage	O
of	O
the	O
dual-ported	O
implementation	O
of	O
this	O
block	O
on	O
Xilinx	O
FPGAs	B-Architecture
.	O
</s>
<s>
Xilinx	O
documents	O
the	O
PicoBlaze	B-Device
as	O
requiring	O
just	O
96	O
FPGA	B-Architecture
slices	O
.	O
</s>
<s>
The	O
small	O
implementation	O
size	O
is	O
achieved	O
in	O
part	O
through	O
a	O
fairly	O
rigid	O
separation	O
of	O
the	O
instruction	O
sequencing	O
side	O
(	O
program	O
counter	O
,	O
call-return	O
stack	O
,	O
implied	O
stack	O
pointer	O
,	O
and	O
interrupt	O
enable	O
bit	O
)	O
from	O
the	O
execution	O
side	O
(	O
ALU	O
,	O
register	O
file	O
,	O
scratchpad	O
RAM	O
,	O
Z/C	O
status	O
bits	O
)	O
.	O
</s>
<s>
The	O
PicoBlaze	B-Device
is	O
poorly	O
suited	O
to	O
programming	O
in	O
compiled	O
languages	O
such	O
as	O
C	B-Language
.	O
In	O
addition	O
to	O
the	O
lack	O
of	O
support	O
for	O
function	O
pointers	O
,	O
there	O
are	O
no	O
instructions	O
or	O
addressing	O
modes	O
to	O
expedite	O
a	O
stack-based	O
calling	O
convention	O
.	O
</s>
<s>
For	O
PicoBlaze	B-Device
it	O
takes	O
two	O
instructions	O
to	O
implement	O
PUSH	O
or	O
POP	O
and	O
two	O
instructions	O
to	O
implement	O
relative	O
addressing	O
off	O
a	O
software-designated	O
stack	O
pointer	O
.	O
</s>
<s>
The	O
PicoBlaze	B-Device
is	O
better	O
suited	O
to	O
a	O
hand-optimized	O
register-based	O
calling	O
convention	O
.	O
</s>
<s>
This	O
does	O
not	O
preclude	O
the	O
use	O
of	O
a	O
Forth-like	O
data	O
stack	O
,	O
and	O
in	O
fact	O
the	O
PicoBlaze	B-Device
is	O
well	O
suited	O
to	O
this	O
approach	O
,	O
if	O
the	O
64-byte	O
scratchpad	O
memory	O
offers	O
sufficient	O
space	O
.	O
</s>
