Knowledge Base Article
While in reset (XRES held high), if key “AC52” is pushed to ISSP bus CY8C20X36A/46A/66A/96A parts will enter into device test mode. In this mode internal regulator of the chip will be disabled and the core of the controller will be powered at a higher voltage than spec’d, thus damaging the device.
Avoiding/Solving this problem requires avoiding CY8C20X36A/46A/66A/96A chip from seeing the “AC52” key in reset condition, which in turn is possible if ISSP lines of CY8C20X36A/46A/66A/96A are not shared.
Note: Cypress do not recommend sharing ISSP bus of CY8C20X36A/46A/66A/96A parts with other PSoC devices