CC1010-RTR1 datasheet(95/152 Pages) TI

95 / 152 page

CC1010

SWRS047

Page 95 of 152

17.8 Transmitting and receiving data

In the Transparent or UART modes

outgoing and incoming data is routed

directly to the modulator in transmit mode

and directly from the demodulator in

receive mode. In the NRZ and Manchester

modes, however, data buffering occurs in

RFBUF as illustrated in Figure 24. This

buffering has some repercussions that

must be considered when receiving or

transmitting data, particularly in bytemode.

RFBUF

8-bit shift reg.

8051 core

Transmitter

Modulator

Receiver

Demodulator

LSB

Figure 24. RF Data Buffering. Dotted lines show bitmode

RFBUF (0xC9) - RF Data Buffer

Bit

Name

R/W

Reset value

Description

7:0

RFBUF

R/W

0x00

RF Data Buffer, 8 bits.

RFBUF is used as described below.

17.8.1

Transmission

When transmitting data in bytemode

(RFCON.BYTEMODE=1),

the

buffering

scheme shifts out bits of an 8-bit shift

MSB first, at periods specified by the

selected baud rate. When this shift register

is empty it will load a new byte from

RFBUF and continue shifting out bits. The

contents of the RFBUF register remain

unchanged after a shift register load. An

interrupt request is generated (EXIF.RFI)

so that RFBUF can be loaded with a new

data byte.

If a new byte is not written within eight bit

periods (eight baud periods in NRZ mode

and 16 baud periods in Manchester

mode), the next time the shift register is

empty it will load the same byte from

RFBUF again. E.g. when transmitting a

preamble consisting of alternating '0' and

'1', it is only necessary to write the byte to

RFBUF once and then wait the desired

number of byte cycles for the preamble to

be transmitted.

In bitmode (RFCON.BYTEMODE=0), the

same buffering occurs, but only for one bit

at a time. Thus, the shift register will load a

new

bit

from

RFBUF.0

after

each

transmitted bit, which in turn generates a

RF-interrupt request so that a new bit can

be loaded. In order to be able to write the

next bit to RFBUF.0 within one bit period

at high baud rates, it is advisable to use a

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