Mentor v8.6_4 manual Add Lfsr Connections, ADD LFsr Connections primarypin lfsrname position

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.

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 Figure 2-1.

SR

Tapping Point

SR

IN MISR

Figure 2-1. MISR placement

You can use the Report LFSRs command to display all the LFSRs with their current values and tap positions.

You use this command primarily for simulating Built-In Self Test (BIST) circuitry.

2-72 FastScan and FlexTest Reference Manual, V8.6_4