Texas Instruments SimpleLink CC2620 Technical Reference Manual page 1476

Radio Doorbell
23.2.3.1 Compare and Capture Events
The available channels may be set up in compare mode or capture mode.
Compare mode can be set up using the CMD_SET_RAT_CMP command (see
case, the timer generates an interrupt when the counter reaches the value given by compareTime. The
interrupt is mapped to RFHWIFG (see
channels, the interrupt flags in use are RATCH5, RATCH6, and RATCH7. Optionally, it is also possible to
control an I/O pin when the counter reaches the value given by compareTime (see
When the CMD_SET_RAT_CMP command has been sent, the value of compareTime is stored in the
radio channel value register (RATCHnVAL) corresponding to the selected channel (see
Capture mode can be used to capture a transition on an input pin and record the RAT counter value at the
time when the transition occurred. Compare mode can be set up using the CMD_SET_RAT_CPT
command (see Section
the RATCHnVAL register corresponding to the selected channel (see
generates an interrupt. As for compare mode, the interrupt is mapped to RFHWIFG. For the available RAT
channels, the interrupt flags in use are RATCH5, RATCH6, and RATCH7. If single-capture mode is
configured in CMD_SET_CPT, only the first transition is captured, unless the channel is armed again, as
explained in the following paragraph. If repeated mode is configured, every transition is captured.
NOTE: In this case, the captured value in RATCHnVAL register may be overwritten at any time if a
new transition occurs.
A channel set up in compare mode or single capture mode may be armed or disarmed. When
CMD_SET_RAT_CMP or CMD_SET_RAT_CPT is sent, the channel is armed automatically, and when the
capture or compare event occurs, the channel is disarmed automatically. A disarmed channel does not
produce any interrupt or cause any timer value to be captured. In addition, a channel may be armed or
disarmed using CMD_ARM_RAT_CH or CMD_DISARM_RAT_CH (see
Section 23.3.4.15). While disarmed, the channel keeps its configuration. To disable a channel that is not
going to be re-armed with the same configuration, the CMD_DISABLE_RAT_CH command may be used
(see Section 23.3.4.12).
23.2.3.2 Radio Timer Outputs
The RAT module has four controllable outputs, RAT_GPO0 through RAT_GPO3. These signals may be
controlled by one of the RAT channels and mapped to signals available for the IOC using the
SYSGPOCTL register (see
transmitter and is controlled internally by the radio CPU (see
may be configured using the CMD_SET_RAT_OUTPUT command (see
output modes decide the transition of the output when an interrupt occurs on the chosen RAT channel
except for the always-0 and always-1 configurations, which take effect immediately and may be used for
initialization.
23.2.3.3 Synchronization With Real-time Clock
When the radio is powered down, the RAT module is not counting. To keep a consistent time base over
time for synchronized protocols, it is possible to synchronize the radio timer with the real-time clock (RTC)
(see Chapter 14, Real-Time Clock).
To allow synchronization after power up, the CMD_SYNC_STOP_RAT command (see
Section 23.3.3.1.10) must be sent before RF core is powered down. This command (until the next RTC
tick) stops the radio timer and returns a parameter rat0, should be stored and provided when the radio
timer is restarted.
The next time the RF core is powered up and the RAT is started, this synchronization must be done using
CMD_SYNC_START_RAT (see
CMD_SYNC_STOP_RAT must be provided. This command starts the RAT, waits for an RTC tick, and
adjusts the RAT. Depending on the application, it may not be necessary to run the
CMD_SYNC_STOP_RAT command every time the radio is powered down; a previous value of rat0 may
be reused. In some cases, however, this may cause issues if the radio has been powered for a long time
and the low-frequency and high-frequency crystal oscillators have a significant error relative to each other.
1476
Radio
Section 23.2.2.2
23.3.4.11). When the transition occurs, the current value of the RAT is stored in
Section 23.8.2.9). The signal RAT_GPO0 is reserved for starting the
Section 23.3.3.1.11), where the rat0 parameter obtained from
Copyright © 2015, Texas Instruments Incorporated
Section
and Section 23.8.2.3). For the available RAT
Table 23-154), and the timer
Section 23.3.4.14
Section 23.3.2.8). The other three signals
Section 23.3.4.11). The different
SWCU117C – February 2015 – Revised September 2015
Submit Documentation Feedback
www.ti.com
23.3.4.10). In this
Section 23.2.3.2).
Table 23-154).
through