AN 425: Using the Command-Line Jam STAPL Solution for Device Programming

ID 683089
Date 12/09/2016
Document Table of Contents

1.6.4. Add External Resistors to Pull the Outputs to a Defined Logic Level

During programming or configuration, you must add external resistors to the output pins to pull the outputs to a defined logic level.

The output pins tri-state during programming or configuration. Additionally, on MAX® 7000, FLEX® 10K, APEX™ 20K, and all configuration devices, the pins are pulled up by a weak internal resistor—for example, 50 kΩ.

However, not all Altera devices have weak pull-up resistors during ISP or in-circuit reconfiguration. For information about which device has weak pull-up resistors, refer to the data sheet of the relevant device family.

Note: Altera recommends that you tie the outputs that drive sensitive input pins to the appropriate level using an external resistor on the order of 1 kΩ. You may need to analyze each of the preceding board layout elements further, especially signal integrity. In some cases, analyze the loading and layout of the JTAG chain to determine whether you need to use discrete buffers or a termination technique.

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