System Considerations
MC1321x Reference Manual, Rev. 1.6
3-22
Freescale Semiconductor
3.10.3
RF Control Output CT_Bias
CT_Bias is a useful signal for interface with external RF components. It must be enabled via the ct_bias_en
control bit, and then its state is determined first by the selected RF mode and then by the active state of the
radio, i.e., whether a TX or RX operation is active:
•
Single Port Operation - In this mode, the CT_Bias can be used to establish the proper DC bias
voltage to a balun depending on the RX state versus TX state as described in
. Note that in single port operation, the ct_bias_inv has no effect and
CT_Bias is at VDDA for TX and is at ground for RX
•
Dual Port Operation - In this mode, the CT_Bias can be used as a control signal to enable an LNA
or to determine the direction of an antenna switch as described in
. In dual port operation ct_bias_inv is used to control the sense of the output control,
i.e., CT_Bias can be active high or active low for TX and vice-versa for RX
defines the CT_Bias output state depending on control bits and operation mode of the modem.
Note that the output state is also defined for the modem low power states of Idle, Hibernate, and Doze as
well as RX and TX operation.
Table 3-6. RF Interface Control Bits
Bit
Designation
Default
Operation
14
ct_bias_en
0
1 = CT_Bias enabled. Output state is defined by
0 = CT_Bias disabled. Output state is tri-stated.
13
ct_bias_inv
0
The output state of CT_Bias under varying conditions is defined in
.
This bit only has effect for dual port operation.
1 = CT_Bias inverted.
0 = CT_Bias not inverted
12
RF_switch_mode
0
1= Single Port Mode selected where RF switch is active and RFIN_M and
RFIN_P and bidirectional signals.
0 = Dual Port Mode selected where RFIN_M and RFIN_P are inputs only and
PAO_P and PAO_N are separate outputs.
(This is default operation).
Table 3-7. CT_Bias Output vs. Register Settings
Mode
CT_Bias_en
RF_switch_mode
CT_Bias_inv
CT_Bias
RX
1
1
0
0
RX
1
1
1
0
RX
1
0
0
0
RX
0
X
X
Hi-Z
RX
1
1
0
1
TX
1
1
0
1
TX
1
1
1
1
TX
1
0
0
1
Содержание freescale semiconductor MC13211
Страница 40: ...MC1321x Pins and Connections MC1321x Reference Manual Rev 1 6 2 6 Freescale Semiconductor...
Страница 100: ...MC1321x Serial Peripheral Interface SPI MC1321x Reference Manual Rev 1 6 4 24 Freescale Semiconductor...
Страница 166: ...Modem Modes of Operation MC1321x Reference Manual Rev 1 6 7 22 Freescale Semiconductor...
Страница 172: ...Modem Interrupt Description MC1321x Reference Manual Rev 1 6 8 6 Freescale Semiconductor...
Страница 186: ...MCU Modes of Operation MC1321x Reference Manual Rev 1 6 10 8 Freescale Semiconductor...
Страница 208: ...MCU Memory MC1321x Reference Manual Rev 1 6 11 22 Freescale Semiconductor...
Страница 244: ...MCU Parallel Input Output MC1321x Reference Manual Rev 1 6 13 20 Freescale Semiconductor...
Страница 288: ...MCU Central Processor Unit CPU MC1321x Reference Manual Rev 1 6 15 20 Freescale Semiconductor...
Страница 308: ...MCU Timer PWM TPM Module MC1321x Reference Manual Rev 1 6 17 16 Freescale Semiconductor...
Страница 338: ...Inter Integrated Circuit IIC MC1321x Reference Manual Rev 1 6 19 14 Freescale Semiconductor...
Страница 372: ...Development Support MC1321x Reference Manual Rev 1 6 21 20 Freescale Semiconductor...