Datasheet

Revision 1.5 Page 17 of 41
nRF905 Product Specification
4. If AUTO_RETRAN is set high, the nRF905 continuously retransmits the packet until TRX_CE is
set low.
5. When TRX_CE is set low, the nRF905 finishes transmitting the outgoing packet and then sets
itself into standby mode.
If TX_EN is set low while TRX_CE is kept high, the nRF905 finishes transmitting the outgoing packet and
enters RX mode in the channel already programmed in the RF-CONFIG register.
The ShockBurst™ mode ensures that a transmitted packet that has started always finishes regardless of
what TRX_EN and TX_EN are set to during transmission. The new mode is activated when the transmis-
sion is completed.
For test purposes such as antenna tuning and measuring output power it is possible to set the transmitter
so that a constant carrier is produced. To do this, TRX_CE must be maintained high instead of being
pulsed and Auto Retransmit should be switched off. After the burst of data is sent the device continues to
send the unmodulated carrier.
Figure 3. Flowchart ShockBurst™ transmit of nRF905.
Note: When DR is set high it can be set low again under the following conditions:
•If TX_EN is set low
•If PWR_UP is set low
SPI - programming
uController loading ADDR
and PAYLOAD data
(Configuration register if
changes since last TX/RX)
NO
YES
nRF ShockBurst TX
Generate CRC and preamble
Sending packet
DR is set high when completed
Transmitter is
powered up
TRX_CE
= HI ?
AUTO_
RETRAN
= HI ?
YES
NO
YES
NO
ADDR PAYLOAD
Data Packet
Bit in configuration
register
TRX_CE
= HI ?
Radio in Standby
TX_EN = HI
PWR_UP = HI
TRX_CE = LO
ADDR PAYLOAD CRC
Pre-
amble
DR is
set low
after pre-
amble