Datasheet

PN532_C1 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2017. All rights reserved.
Product data sheet
COMPANY PUBLIC
Rev. 3.6 — 28 November 2017
115436 129 of 222
NXP Semiconductors
PN532/C1
Near Field Communication (NFC) controller
8.6.16.3 Status information about the FIFO buffer
The 80C51may obtain the following data about the FIFO-buffers status:
• Number of bytes already stored in the FIFO-buffer: FIFOLevel[6:0] in register
CIU_FIFOLevel
• Warning, that the FIFO-buffer is quite full: HiAlert in register CIU_Status1
• Warning, that the FIFO-buffer is quite empty: LoAlert in register CIU_Status1
• Indication, that bytes were written to the FIFO-buffer although it was already full:
BufferOvfl in register CIU_Error.
BufferOvfl can be set to logic 0 only by setting to logic 1 bit FlushBuffer in the register
CIU_FIFOLevel.
The CIU can generate an interrupt signal
• If LoAlertIEn in register CIU_CommIEn is set to logic 1, it will set to logic 1 CIU_IRQ_0
in the register CIU_Status1, when LoAlert in the same register changes to logic 1.
• If HiAlertIEN in register CIU_CommIEn is set to logic 1, it will set to logic 1 CIU_IRQ_0
in the register CIU_Status1, when HiAlert in the same register changes to logic 1.
The flag HiAlert is set to logic 1 if only WaterLevel[5:0] bits (as set in register
CIU_WaterLevel) or less can be stored in the FIFO-buffer. It is generated by the following
equation:
The flag LoAlert is set to logic 1 if WaterLevel[5:0] bits (as set in register CIU_WaterLevel)
or less are actually stored in the FIFO-buffer. It is generated by the following equation:
HiAlert 64 FIFOLenght–WaterLevel=
LoAlert FIFOLenght WaterLevel=