The OCDS EV chip is used to emulate the real MCU. It provides an “On-Chip Debug” function to debug the real MCU device during the development process. The EV chip and the real MCU device are almost functionally compatible except for
the “On-Chip Debug” function.
Users can use the OCDS EV chip to emulate the real chip device behavior by connecting the OCDSDA and OCDSCK pins to the Holtek HT-IDE development tools. For more detailed information, please refer to the Holtek e-Link for 8-bit MCU OCDS User’s Guide (TDOC0016).

1. When do I need to use the OCDS EV chip?
   When you want to use e-Link for a project development, you need an OCDS EV chip to work with e-Link.
2. How is the OCDS EV chip different from the real MCU?
   OCDS EV chip provides the "On-Chip Debug" function. In terms of pin function, it has the function of OCDSDA and OCDSCK.

3. What is the part number of an OCDS EV chip?
   Usually, the part number of OCDS EV chip has "V", and the part number of real MCU has "F". For example, HT66F2390 is a real MCU, and HT66V2390 is the OCDS EV chip of HT66F2390.
4. What is the pin number of an OCDS EV chip?
   The OCDS EV chip has the same pin number as the real MCU. However, when the real MCU is 8-pin or 10-pin, the OCDS EV chip is 16-pin. In this case, you can use an e-FPCB for pin conversion.
5. The datasheet of an OCDS EV chip?
   There is no dedicated datasheet for OCDS EV chip. It shares the same datasheet with its related real MCU. You can find the OCDS description in the datasheet of a real MCU.
6. Should I modify the program code for mass production after developing with OCDS EV chip?
   It depends on whether you need to use the two pins that provide OCDS function.
   If you require the two pins for your product, you need to write the program code for them.
   In reverse, if these two pins are not required for your product, you don’t need to change the program code.