System Considerations
MC1321x Reference Manual, Rev. 1.6
Freescale Semiconductor
3-21
3.10.2
Controlling RF Modes of Operation
Use of the RF interface pins and RF modes of operation are controlled through several bits of modem
Control_B Register 07.
shows the model for Register 07 with the RF interface control bits
highlighted.
Figure 3-7. Modem Control_B Register 07 Model
The RF interface control bits include:
•
RF_switch_mode (Bit 12) - This bit selects Dual Port Mode versus Single Port Mode
— The default condition (Bit 12 = 0) is Dual Port Mode where the RF inputs are RFIN_M and
RFIN_P and the RF outputs are PAO_M and PAO_P and operation is as described in
Section 3.10.1.2, “Dual Port Operation”
. The use of CT_Bias pin in Dual Port Mode in
controlled by Bit 13 and Bit 12
— When Bit = 1, the Single Port Mode is selected where RFIN_M (PAO_M) and RFIN_P
(PAO_P) become bidirectional pins and operation is as described in
. The use of CT_Bias pin in Single Port Mode is controlled by Bit 14 and
operation of the radio
•
ct_bias_en (Bit 14) - This bit is the enable for the CT_Bias output. When Bit 14 = 0 (default), the
CT_Bias is disabled and stays in a Hi-Z or tri-stated condition. When Bit 14 = 1 the CT_Bias output
is active and its state is controlled by the selected mode (Bit 12), ct_bias_inv, and operation of the
radio
•
ct_bias_inv (Bit 13) - This bit only affects the state of CT_Bias when Dual Port Mode is selected
and CT_Bias is active. The CT_Bias changes state in Dual Port Mode based on the TX or RX state
of the radio. The ct_bias_inv bit causes the sense of the active state to change or invert based on
Bit 13’s setting. In this manner the user can select the CT_Bias as a control signal for external
components and make the control signal active high or active low
summarizes the operation of the RF interface control bits.
Register 07
0x07
BIT
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
tmr_load
ct
_b
ias
_
e
n
ct_bi
as_in
v
RF
_swi
tch_
mo
de
miso
_hiz_
en
clko_d
oze_e
n
tx_
done
_mask
rx_
don
e_mask
use_
strm_mode
hib
_en
do
ze
_e
n
TYPE
r/w r/w r/w r/w r/w
r/w
r/w r/w r/w
r/w
r/w
RESET
0
0
0
0
1
1
0
0
0
0
0
0
0
0
0
0
0x0C00
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