Xilinx Constraints Guide

Chapter 4: Xilinx Constraints
CONFIG_MODE (Configuration Mode)
Architecture Support
Applicable Elements
Propagation Rules
The CONFIG_MODE (Configuration Mode) constraint:
• Communicates to PAR which of the dual purpose configuration pins can be used
as general purpose IOs.
• Is used by PAR to prohibit the use of Dual Purpose IOs if they are
required for CONFIG_MODE: S_SELECTMAP+READBACK or
M_SELECTMAP+READBACK. The bitgen -g Persist option must be used to retain
these IO for Readback and Reconfiguration use.
In the case of CONFIG_MODE: S_SELECTMAP or M_SELECTMAP, PAR uses the
Dual Purpose IOs as General Purpose IOs only if necessary.
Applies to Spartan®-3, Virtex®-4, Virtex-5, Virtex-6, and 7 series devices.
Attaches to the CONFIG symbol.
Applies to dual-purpose I/Os.
Syntax Examples
The following examples show how to use this constraint with particular tools or
methods. If a tool or method is not listed, you cannot use this constraint with it.
UCF Syntax
CONFIG CONFIG_MODE=string;
where
string can be one of the following:
• M_SERIAL
Master Serial Mode (The default value)
• S_SERIAL
Slave Serial Mode
• B_SCAN
Boundary Scan Mode
• B_SCAN+READBACK
Boundary Scan Mode with Persist expected.
• M_SELECTMAP
Master SelectMAP Mode , 8-bit width
• M_SELECTMAP+READBACK
Master SelectMAP Mode, 8-bit width, with Persist expected.
• S_SELECTMAP
Slave SelectMAP Mode, 8-bit width
• S_SELECTMAP+READBACK
Slave SelectMAP Mode, 8-bit width, with Persist expected.
Constraints Guide
86 www.xilinx.com UG625 (v. 13.2) July 6, 2011