CC2550-RTR1 datasheet(32/55 Pages) TI

32 / 55 page

CC2550

PRELIMINARY Data Sheet (Rev.1.2)

SWRS039A

Page 32 of 54

Asynchronous and Synchronous Serial Operation

Several features and modes of operation have

been included in the

CC2550 to provide

backward compatibility with previous Chipcon

products and other existing RF communication

systems. For new systems, it is recommended

to use the built-in packet handling features, as

they can give more robust communication,

significantly offload the microcontroller and

simplify software development.

25.1

Asynchronous operation

For backward compatibility with systems

already using the asynchronous data transfer

from other Chipcon products, asynchronous

transfer is also included in

CC2550. When

asynchronous transfer is enabled, several of

the support mechanisms for the MCU that are

included in

CC2550 will be disabled, such as

packet handling hardware, buffering in the

FIFO and so on. The asynchronous transfer

mode does not allow the use of the data

whitener, interleaver and FEC.

Only FSK, GFSK and OOK are supported for

asynchronous transfer.

Setting

PKTCTRL0.PKT_FORMAT

enables asynchronous transparent (serial)

mode.

In TX, the GDO0 pin is used for data input (TX

data).

The MCU must control start and stop of

transmit with the STX and SIDLE strobes.

The

CC2550 modulator samples the level of the

asynchronous input 8 times faster than the

programmed data rate. The timing requirement

for the asynchronous stream is that the error in

the bit period must be less than one eighth of

the programmed data rate.

25.2

Synchronous serial operation

Setting

PKTCTRL0.PKT_FORMAT

enables synchronous serial operation mode. In

this operational mode the data must be NRZ

encoded (MDMCFG2.MANCHESTER_EN=0). In

synchronous serial operation mode, data is

transferred on a two wire serial interface. The

CC2550 provides a clock that is used to set up

new data on the data input line. Data input (TX

data) is the GDO0 pin. This pin will

automatically be configured as an input when

TX is active.

Preamble and sync word insertion may or may

not be active, dependent on the sync mode set

by the MDMCFG3.SYNC_MODE. If preamble and

sync word is disabled, all other packet handler

features and FEC should also be disabled.

The MCU must then handle preamble and

sync word insertion in software. If preamble

and sync word insertion is left on, all packet

handling features and FEC can be used. The

CC2550 will insert the preamble and sync word

and the MCU will only provide the data

payload.

This

equivalent

the

recommended FIFO operation mode.

26 System considerations and Guidelines

26.1

SRD Regulations

International regulations and national laws

regulate the use of radio receivers and

transmitters. Short Range Devices (SRDs) for

license free operation are allowed to operate

in the 2.45 GHz bands worldwide. The most

important regulations are EN 300 440 and EN

300 328 (Europe), FCC CFR47 part 15.247

and 15.249 (USA), and ARIB STD-T66

(Japan). A summary of the most important

aspects of these regulations can be found in

Application Note AN032 SRD regulations for

license-free transceiver operation in the 2.4

GHz band

, available from the TI and Chipcon

websites.

Please note that compliance with regulations

dependent

complete

system

performance. It is the customer’s responsibility

to ensure that the system complies with

regulations.

26.2

Frequency

Hopping

and

Multi-

Channel Systems

The 2.400 – 2.4835 GHz band is shared by

many systems both in industrial, office and

home

environments.

therefore

recommended to use frequency hopping

spread spectrum (FHSS) or a multi-channel

protocol because the frequency diversity

makes the system more robust with respect to

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