Mentor v8.6_4 User Manual
FastScan and FlexTest Reference Manual, V8.6_4
2-72
Add LFSR Connections
Command Dictionary
Add LFSR Connections
Tools Supported: FastScan
Scope: Setup mode
Usage
ADD LFsr Connections primary_pin lfsr_name position...
Description
Connects an external pin to a Linear Feedback Shift Register (LFSR).
The Add LFSR Connections command connects a core logic pin to an LFSR. You
specify this pin with the primary_pin argument. LFSR bit positions have integer
numbers, where 0 indicates the least significant bit position. FastScan assumes
that the output of the 0 bit position connects to the input of the highest bit position.
If you select multiple bits of a Pseudo-Random Pattern Generator (PRPG) for the
position argument, the tool assumes they are all exclusive-ORed together to create
the value for the pin.
specify this pin with the primary_pin argument. LFSR bit positions have integer
numbers, where 0 indicates the least significant bit position. FastScan assumes
that the output of the 0 bit position connects to the input of the highest bit position.
If you select multiple bits of a Pseudo-Random Pattern Generator (PRPG) for the
position argument, the tool assumes they are all exclusive-ORed together to create
the value for the pin.
If you determine that multiple primary_pins must connect to a bit position of a
Multiple Input Signature Register (MISR), you must issue a separate Add LFSR
Connections command for each pin. FastScan assumes the pins are all exclusive-
ORed together to create the value for the next MISR input. FastScan also assumes
that the physical placement of the MISR connections is after the tapping points as
shown in
Multiple Input Signature Register (MISR), you must issue a separate Add LFSR
Connections command for each pin. FastScan assumes the pins are all exclusive-
ORed together to create the value for the next MISR input. FastScan also assumes
that the physical placement of the MISR connections is after the tapping points as
shown in
.
Figure 2-1. MISR placement
You can use the Report LFSRs command to display all the LFSRs with their
current values and tap positions.
current values and tap positions.
You use this command primarily for simulating Built-In Self Test (BIST)
circuitry.
circuitry.
SR
SR
IN
MISR
Tapping Point