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 mode enabled

Fixed packet length mode anbled when

less than 256 bytes remains of packet

600 bytes transmitted

Length field transmitted. PKTLEN set to

mod(600, 256) = 88

CC115L

SWRS105B – MAY 2011 – REVISED JUNE 2014

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Fixed packet length mode is selected by setting PKTCTRL0.LENGTH_CONFIG=0. The desired packet

length is set by the PKTLEN register. This value must be different from 0.

In variable packet length mode, PKTCTRL0.LENGTH_CONFIG=1, the packet length is configured by the

first byte transmitted after the sync word. The packet length is defined as the payload data, excluding the

length byte and the optional CRC. The PKTLEN value must be different from 0.

With PKTCTRL0.LENGTH_CONFIG=2, the packet length is set to infinite and transmission will continue

until turned off manually. As described in , this can be used to support packet formats with different length

configuration than natively supported by CC115L. One should make sure that TX mode is not turned off

during the transmission of the first half of any byte. Refer to the CC115L Errata Notes SWRZ036 for more

details.

NOTE

The minimum packet length supported (excluding the optional length byte and CRC) is one

byte of payload data.

5.8.1.1

Packet Length > 255

The packet automation control register, PKTCTRL0, can be reprogrammed during TX. This opens the

possibility to transmit packets that are longer than 256 bytes and still be able to use the packet handling

hardware

support.

At

the

start

of

the

packet,

the

infinite

packet

length

mode

(

PKTCTRL0.LENGTH_CONFIG=2) must be active and the PKTLEN register is set to mod(length, 256).

When less than 256 bytes remains of the packet, the MCU disables infinite packet length mode and

activates fixed packet length mode ( PKTCTRL0.LENGTH_CONFIG=0). When the internal byte counter

reaches the PKTLEN value, the transmission ends (the radio enters the state determined by

TXOFF_MODE).

Automatic

CRC

appending/checking

can

also

be

used

(by

setting

PKTCTRL0.CRC_EN=1).

When for example a 600-byte packet is to be transmitted, the MCU should do the following (see Figure 5-

7).

•

Set PKTCTRL0.LENGTH_CONFIG=2.

•

Pre-program the PKTLEN register to mod(600, 256) = 88.

•

Transmit at least 345 bytes (600 - 255), for example by filling the 64-byte TX FIFO six times (384 bytes

transmitted).

•

Set PKTCTRL0.LENGTH_CONFIG=0.

•

The transmission ends when the packet counter reaches 88. A total of 600 bytes are transmitted.

Figure 5-7. Packet Length > 255

24

Detailed Description

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