CC2500RGPR Datasheet, PDF(31/99 Page) Texas Instruments – Low-Cost Low-Power 2.4 GHz RF Transceiver

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CC2500RGPR Datasheet, PDF (31/99 Pages) Texas Instruments – Low-Cost Low-Power 2.4 GHz RF Transceiver

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CC2500

ï· Pre-program the PKTLEN register to

mod(600,256)=88.

ï· Transmit at least 345 bytes, for example

by filling the 64-byte TX FIFO six times

(384 bytes transmitted).

ï· Set PKTCTRL0.LENGTH_CONFIG=0.

ï· The transmission ends when the packet

counter reaches 88. A total of 600 bytes

are transmitted.

Internal byte counter in packet handler counts from 0 to 255 and then starts at 0 again

0,1,..........,88,.................... 255,0,........,88,.................. ,255,0,........,88,.................. ,255,0,.......................

Infinite packet length enabled

Fixed packet length

enabled when less than

256 bytes remains of

packet

600 bytes transmitted and

received

Length field transmitted and received. Rx and Tx PKTLEN value set to mod(600,256) = 88

Figure 12: Packet Length > 256

15.3 Packet Filtering in Receive Mode

CC2500 supports three different types of

packet-filtering: address filtering, maximum

length filtering and CRC filtering.

15.3.1 Address Filtering

Setting PKTCTRL1.ADR_CHK to any other

value than zero enables the packet address

filter. The packet handler engine will compare

the destination address byte in the packet with

the programmed node address in the ADDR

PKTCTRL1.ADR_CHK=10b or both 0x00 and

0xFF broadcast addresses when

PKTCTRL1.ADR_CHK=11b. If the received

address matches a valid address, the packet is

received and written into the RX FIFO. If the

address match fails, the packet is discarded

and receive mode restarted (regardless of the

MCSM1.RXOFF_MODE setting).

If the received address matches a valid

address when using infinite packet length

mode and address filtering is enabled, 0xFF

will be written into the RX FIFO followed by the

address byte and then the payload data.

15.3.2 Maximum Length Filtering

In variable packet length mode,

PKTCTRL0.LENGTH_CONFIG=1,

the

PKTLEN.PACKET_LENGTH register value is

used to set the maximum allowed packet

length. If the received length byte has a larger

value than this, the packet is discarded and

receive mode restarted (regardless of the

MCSM1.RXOFF_MODE setting).

15.3.3 CRC Filtering

The filtering of a packet when CRC check fails

enabled

setting

PKTCTRL1.CRC_AUTOFLUSH=1. The CRC

auto flush function will flush the entire RX

FIFO if the CRC check fails. After auto flushing

the RX FIFO, the next state depends on the

MCSM1.RXOFF_MODE

setting.

PKTCTRL0.CC2400_EN must be 0 (default)

for the CRC auto flush function to work

correctly.

When using the auto flush function, the

maximum packet length is 63 bytes in variable

packet length mode and 64 bytes in fixed

packet length mode. Note that the maximum

allowed packet length is reduced by two bytes

when PKTCTRL1.APPEND_STATUS is

enabled, to make room in the RX FIFO for the

two status bytes appended at the end of the

packet. Since the entire RX FIFO is flushed

when the CRC check fails, the previously

received packet must be read out of the FIFO

before receiving the current packet. The MCU

must not read from the current packet until the

CRC has been checked as OK.

15.4 CRC Check

There are two different CRC implementations.

PKTCTRL0.CC2400_EN selects between the

2 options. The CRC check is different for the 2

SWRS040C

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