Reset Mode and Power Cycle Mode in ISSP

Question: What are Reset mode and Power Cycle mode of Programming? When should I use them?

Answer: In the power cycle mode, the programmer applies VDD to the target PSoC device and within a specified time frame sends some commands to the PSoC over the ISSP SCLK and SDATA lines and puts it into programming mode. In the Reset mode, the programmer generates a reset on the XRES pin of the PSoC and sends the commands within a time frame to put the PSoC into programming mode. Refer Application note AN2026A - In-System Serial Programming (ISSP) Protocol for details on the Acquire Device phase.

Power cycle mode of programming can be used to program any PSoC device. There are a few points to remember while using the Power cycle mode.

When the device is programmed in power cycle mode, the programmer supplies VDD to the PSoC. Any circuit connected to the PSoC's VDD will also be powered by the Programmer and will draw power from the Programmer. Care should be taken in not exceeding the Programmer's current limit.
If the target board has components working on 3.3V or below and if the Programmer is capable of only 5V (for example, the CY3210 MiniProg1 programmer), this will damage the components on the board. Under such situation Reset programming has to be used.

In Reset mode, the target PSoC should be initially supplied with VDD and the programming should be initiated. If VDD is not supplied to PSoC, the programmer will not be able to acquire the target. Reset mode is not possible on PSoC devices without the XRES pin (for example 8 pin PSoC devices). For these devices use Power cycle mode.

Tags: PSoC1 ISSP

Comments (1)

|75.67.223.xxx |2009-11-25 12:52:46 danadak - PROC Devices

If you are working with PROC parts you need to always select Reset mode to prevent Programmer from applying 5V to PROC device, as it is a 3.6 V device. Otherwise you will toast the PROC device. Note that Reset IS NOT the default programmer mode, so you have to consciously make the selection.

Regards, Dana

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