This part of IEC 62566 provides requirements for achieving highly reliable HDL-Programmed Devices (HPDs), for use in I&C systems of nuclear power plants performing functions of safety category B or C as defined by IEC 61226. The programming of HPDs relies on Hardware Description Languages (HDL) and related software tools. They are typically based on blank Field Programmable Gate Arrays (FPGAs) or similar micro-electronic technologies such as Programmable Logic Devices (PLD), Complex Programmable Logic Devices (CPLDs), etc. General purpose integrated circuits such as microprocessors are not HPDs. Annex B.8 provides descriptions of a number of different types of integrated circuits. This document provides requirements on: a dedicated HPD life-cycle addressing each phase of the development of HPDs, including specification of requirements, design, implementation, integration and validation, as well as verification activities associated with each phase, planning and complementary activities such as modification and production, selection of pre-developed components. This includes micro-electronic technologies and Pre-Developed Blocks (PDBs), tools used to design, implement and verify HPDs. This document does not put requirements on the development of the micro-electronic technologies, which are usually available as \'commercial off-the-shelf\' items and are not developed under nuclear quality assurance standards. It addresses the developments made with these micro-electronic technologies in an I&C project with HDLs and related tools. This document provides guidance to avoid as far as possible latent faults remaining in HPDs, and to reduce the susceptibility to single failures as well as to potential Common Cause Failures (CCFs). Reliability aspects related to environmental qualification and failures due to ageing or physical degradation are not handled in this document. Other standards, especially IEC 60987, IEC/IEEE 60780-323 and IEC 62342, address these topics. This document does not cover cybersecurity for HDL aspects of I&C systems. IEC 62645 provides requirements for security programmes for I&C programmable digital systems. This document provides guidance and requirements to produce verifiable HPD designs and implementations requiring justification due for their role in carrying out category B or C safety functions. This document describes the activities to develop HPDs, organized in the framework of a dedicated life-cycle. It also describes activities and guidelines to be used in addition to the requirements of IEC 61226 for system classification and IEC 61513 for system integration and validation when HPDs are included.