Datasheet

Table Of Contents

Product data sheet

COMPANY PUBLIC

Rev. 3.6 — 28 November 2017

115436 133 of 222

NXP Semiconductors

PN532/C1

Near Field Communication (NFC) controller

8.6.19.3 Transmitter Power-down

The Transmitter Power-down mode switches off the internal antenna drivers to turn off the

RF field by setting the bits Tx1RFEn and Tx2RFEn in the register CIU_TxControl to logic

0. The receiver is still switched on, meaning the CIU can be accessed by a second NFC

device as a NFCIP-1 target.

Note: In case the bit InitialRFOn has been set to logic 1, when the drivers were already

switched on, it is needed either to set InitialRFOn to logic 0, before setting the bits

Tx1RFEn and Tx2RFEn in the register CIU_TxControl to logic 0, or to set also the bits

Tx1RFAutoEn and Tx2RFAutoEn in the register CIU_TxAuto to logic 0.

8.6.20 CIU command set

8.6.20.1 General description

The CIU behavior is determined by an internal state machine capable to perform a certain

set of commands. Writing the according command code to the CIU_Command register

starts the commands.

Arguments and/or data necessary to process a command are mainly exchanged via the

FIFO buffer.

8.6.20.2 General behavior

• Each command, that needs a data stream (or data byte stream) as input will

immediately process the data it finds in the FIFO buffer. An exception to this rule is the

Transceive command. Using this command the transmission is started with the

StartSend bit in CIU_BitFraming register.

• Each command that needs a certain number of arguments will start processing only

when it has received the correct number of arguments via the FIFO buffer.

• The FIFO buffer is not cleared automatically at command start. Therefore, it is also

possible to write the command arguments and/or the data bytes into the FIFO buffer

and start the command afterwards.

• Each command may be interrupted by the 80C51 by writing a new command code

into the CIU_Command register e.g.: the Idle command.