App note from Holtek on their HT45F4050 device which discuss its hardware and software application. Link here (PDF)
NFC, which is an acronym for Near Field Communication, is a technology allowing wireless connection between devices using a simple touch. NFC technology operates at a frequency of 13.56MHz with an operating distance within 10cm. It has three data rates of 106Kbit/s, 212Kbit/s and 424Kbit/s, and supports three operating modes. These are card emulation, card read/write and P2P. Its operating standard is compatible with Sony’s FeliCa standard (Type F) and Philips’ MIFARE standards (ISO 14443A – Type A; ISO 14443B – Type B).
The HT45F4050 supports a data rate of 106Kbit/s and is mainly used for card emulation. It follows the ISO14443A Type A standard.