eldo_user

Eldo Netlist Setup
Working With Subcircuits and Device Libraries
Working With Subcircuits and Device Libraries
This topic is divided into:
Subcircuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Device Libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Subcircuits
Subcircuits can be used to simplify netlists because once defined they can be instantiated
multiple times in the netlist. Subcircuit definitions and instances can be nested. The inner
subcircuit definitions are local to the subcircuit definition in which they are defined, that is, they
are not valid outside of it. Parameters contained in a subcircuit can be assigned explicitly or via
the .PARAM command.
Subcircuits may be parameterized. Symbols may be used as values within the subcircuit body
which may be assigned values when the subcircuit is instantiated. A subcircuit may be stored in
a library file, in which case the .SUBCKT LIB syntax should be used together with .LIB or
.ADDLIB.
A subcircuit may optionally be simulated using the differentiated accuracy system. The iteration
technique used to process the subcircuit is chosen by the (ANALOG) optional keyword.
Usually, a circuit with (ANALOG) specified indicates ‘high accuracy’.
By default, when Eldo encounters multiple definitions of .SUBCKT statements an error is
reported and the simulation is stopped. To enable the simulation to proceed you can force Eldo
to only use the first definition by specifying option USEFIRSTDEF at the beginning of the
netlist (any further definitions are ignored); or to only use the last definition specify option
USE_LAST_SUBCKT or USELASTDEF (any previous definitions are ignored). The last
definition takes into account contents included from library files.
Order of Precedence of Subcircuit Parameter Assignments
Parameters used within a subcircuit may be defined in several ways.
• In the subcircuit instantiation:
X1 N1 N2 N3 MY_SUBCIRCUIT P3=10
• Internally, within the subcircuit:
.SUBCKT MY_SUBCIRCUIT
.PARAM p3=20
.ENDS
• In the subcircuit declaration:
.SUBCKT MY_SUBCIRCUIT P1 P2 P3 PARAM: p3=2
Eldo® User's Manual, 15.3 127