CC1010-RTR1 datasheet(96/152 Pages) TI

96 / 152 page

CC1010

SWRS047

Page 96 of 152

tight polling loop instead of an interrupt

based transmit procedure.

In order to start transmission of data as

quickly as possible, the first bit/byte to be

transmitted should be written to RFBUF

before

the modulator

turned on

(RFMAIN.TX_PD=0). It will then be

immediately loaded into the shift register

and an interrupt request will be generated

for the second bit/byte.

It is especially important to take the

buffering scheme into account at the end

of a transmission. When the last byte of a

data frame or packet is loaded into the

shift register it is still not transmitted. Thus

the interrupt request generated at the

same time must not turn off either analog

or digital parts of the transmit chain. The

transmission can not be ended safely until

nine bit periods later in bytemode and two

bit periods later in bitmode, when the last

bit has been shifted out and has

propagated through the transmit chain to

the antenna. A simple solution is to always

transmit two extra bytes in bytemode or

two extra bits in bitmode at the end of the

real data content. (In bytemode this will

result in that approximately seven of these

bits will be transmitted along with the real

data.) This should cause no problems in

practice.

17.8.2

Reception

When receiving data the buffering scheme

works in reverse of what it does during

transmitting.

Bit

bit

from

the

demodulator is shifted into the eight-bit

shift register, MSB-first: When the shift

interrupt

request

generated

(EXIF.RFIF). The byte must be read

within one byte period (eight baud periods

in NRZ mode and 16 baud periods in

Manchester mode). If not, it will be

overwritten by the next byte received and

the data is lost.

In bitmode the same buffering occurs, but

only for one bit at a time. Thus, when a

new bit arrives from the demodulator the

shift register will store it and store the last

bit into RFBUF.0, which in turn generates

a RF-interrupt request so that the new bit

can be read. In order to be able to read

the next bit from RFBUF.0 within one bit

period at high baud rates it is advisable to

use a tight polling loop instead of an

interrupt based receive procedure.

No special considerations have to be

taken at the start of, or end of, receptions.

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