Rainbow Electronics ATmega128RFA1 - Manual (Page 113)

113
8266A-MCU Wireless-12/09
ATmega128RFA1
This register bit signals the currently selected antenna path. The selection may be
based either on the last antenna diversity cycle (ANT_DIV_EN = 1) or on the content of
register bits ANT_CTRL.
Table 9-47 ANT_SEL Register Bits
Register Bits Value Description
0 Antenna 0 ANT_SEL
1 Antenna 1
• Bit 6:4 – Res2:0 - Reserved
• Bit 3 – ANT_DIV_EN - Enable Antenna Diversity
If this register bit is set the Antenna Diversity algorithm is enabled. On reception of a
frame the algorithm selects an antenna autonomously during SHR search. This
selection is kept until
1. a new SHR search starts or
2. receive states are left or
3. a manually programming of bits ANT_CTRL occurred. If ANT_DIV_EN = 1 the bit
ANT_EXT_SW_EN shall also be set to 1.
Table 9-48 ANT_DIV_EN Register Bits
Register Bits Value Description
0 Antenna Diversity algorithm disabled ANT_DIV_EN
1 Antenna Diversity algorithm enabled
• Bit 2 – ANT_EXT_SW_EN - Enable External Antenna Switch Control
If enabled, pin DIG1 and pin DIG2 become output pins and provide a differential control
signal for an external Antenna Diversity switch. The selection of a specific antenna is
done either by the automatic Antenna Diversity algorithm (ANT_DIV_EN = 1) or
according to bits ANT_CTRL if the Antenna Diversity algorithm is disabled. Do not
enable Antenna Diversity RF switch control (ANT_EXT_SW_EN = 1) and RX Frame
Time Stamping (IRQ_2_EXT_EN = 1, see register TRX_CTRL_1) at the same time. If
this bit is set the control pins DIG1/DIG2 are activated in all radio transceiver states as
long as bit ANT_EXT_SW_EN is also set. If the radio transceiver is not in a receive or
transmit state, it is recommended to disable bit ANT_EXT_SW_EN to reduce the power
consumption or avoid leakage current of an external RF switch especially during
SLEEP state. The output pins DIG1 and DIG2 are pulled-down to digital ground if bit
ANT_EXT_SW_EN = 0.
Table 9-49 ANT_EXT_SW_EN Register Bits
Register Bits Value Description
0 Antenna Diversity RF switch control disabled ANT_EXT_SW_EN
1 Antenna Diversity RF switch control enabled
• Bit 1:0 – ANT_CTRL1:0 - Static Antenna Diversity Switch Control
These bits provide a static control of an Antenna Diversity switch. This register setting
defines the selected antenna if ANT_DIV_EN is set to 0 (Antenna Diversity disabled).
Register values 1 and 2 are valid for ANT_EXT_SW_EN = 1.
Table 9-50 ANT_CTRL Register Bits
Register Bits Value Description
0 Reserved ANT_CTRL1:0
1 Antenna 1: DIG1=H, DIG2=L