CC1020-RTR1 datasheet(57/95 Pages) TI1

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CC1020

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SWRS046H – NOVEMBER 2006 – REVISED MARCH 2015

PD_MODE[1:0] in the MAIN register should be set to 01. If DCLK_LOCK in the INTERFACE register is set

to 1 the DCLK signal is always logic high if the PLL is not in lock. When the PLL locks to the desired

frequency the DCLK signal changes to logic 0. When this interrupt has been detected write

PD_MODE[1:0] = 00. This will enable the DCLK signal.

This function can be used to wait for the PLL to be locked before the PA is ramped up in transmit mode. In

receive mode, it can be used to wait until the PLL is locked before searching for preamble.

5.18.2 Interrupt Upon Received Signal Carrier Sense

In synchronous mode the DCLK pin on CC1020 can also be used to give an interrupt signal to the

microcontroller when the RSSI level exceeds a certain threshold (carrier sense threshold). This function

can be used to wake or interrupt the microcontroller when a strong signal is received.

Gating the DCLK signal with the carrier sense signal makes the interrupt signal.

This function should only be used in receive mode and is enabled by setting DCLK_CS = 1 in the

INTERFACE register.

The DCLK signal is always logic high unless carrier sense is indicated. When carrier sense is indicated

the DCLK starts running. When gating the DCLK signal with the carrier sense signal at least 2 dummy bits

should be added after the data payload in TX mode. The reason being that the carrier sense signal is

generated earlier in the receive chain (that is, before the demodulator), causing it to be updated 2 bits

before the corresponding data is available on the DIO pin.

In transmit mode DCLK_CS must be set to 0. Refer to CC1020 Errata Note 002, available in the CC1020

product folder.

5.19 PA_EN and LNA_EN Digital Output Pins

5.19.1 Interfacing an External LNA or PA

CC1020 has two digital output pins, PA_EN and LNA_EN, which can be used to control an external LNA

or PA. The functionality of these pins are controlled through the INTERFACE register. The outputs can

also be used as general digital output control signals.

EXT_PA_POL and EXT_LNA_POL control the active polarity of the signals.

EXT_PA and EXT_LNA control the function of the pins. If EXT_PA = 1, then the PA_EN pin will be

activated when the internal PA is turned on. Otherwise, the EXT_PA_POL bit controls the PA_EN pin

directly. If EXT_LNA = 1, then the LNA_EN pin will be activated when the internal LNA is turned on.

Otherwise, the EXT_LNA_POL bit controls the LNA_EN pin directly.

These two pins can therefore also be used as two general control signals, see Section 5.19.2. In the TI

reference design LNA_EN and PA_EN are used to control the external T/R switch.

5.19.2 General Purpose Output Control Pins

The two digital output pins, PA_EN and LNA_EN, can be used as two general control signals by setting

EXT_PA = 0 and EXT_LNA = 0. The output value is then set directly by the value written to EXT_PA_POL

and EXT_LNA_POL.

The LOCK pin can also be used as a general-purpose output pin. The LOCK pin is controlled by

LOCK_SELECT[3:0] in the LOCK register. The LOCK pin is low when LOCK_SELECT[3:0] = 0000, and

high when LOCK_SELECT[3:0] = 0001.

These features can be used to save I/O pins on the microcontroller when the other functions associated

with these pins are not used.

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