+
INT REQn
DMA REQy
=
From counter
block 0
From counter
block 1
31
0
Update Compare
RTIUDCP0
/
RTIUDCP1
RTIUDCP2
/
RTIUDCP3
Compare
RTICOMP0
/
RTICOMP1
RTICOMP2
/
RTICOMP3
31
0
32
Control
RTICOMPCTRL
32
32
1
Enable/Disable
RTISETINTENA[3:0]
RTICLEARINTENA[3:0]
Enable/Disable
RTISETINTENA[11:8]
RTICLEARINTENA[11:8]
Module Operation
588
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
Real-Time Interrupt (RTI) Module
Figure 17-3. Compare Unit Block Diagram (shows only 1 of 4 blocks for simplification)
Another interrupt that can be generated is the overflow interrupt (OVLINTx) in case the RTIFRCx counter
overflows.
The interrupts/DMA requests can be enabled in the RTISETINTENA register and disabled in the
RTICLEARINTENA register. The RTIINTFLAG register shows the pending interrupts.
17.2.3 RTI Clocking
The counter blocks are clocked with RTICLK (for definition see
). Counter block 0 can be
clocked in addition by either the FlexRay Macrotick (NTU0) or the FlexRay Start of Cycle (NTU1).
A clock supervision for the NTUx clocking scheme is implemented to avoid missing operating system ticks.
17.2.4 Synchronizing Timer Events to Network Time (NTU)
For applications which are participating on a time-triggered communication bus, it is often beneficial to
synchronize the application or operating system to the network time. The RTI provides a feature to
increment Free Running Counter 0 (RTIFRC0) by a periodic clock provided by the communication module.
In this case two different clocks can be chosen. One is the FlexRay module Macrotick (NTU0) and the
other is the Start of Cycle (NTU1) information of the same module.
The application has control over which clock (RTICLK, NTU0, NTU1) should be used for clocking
RTIFRC0. If NTUx is used, a clock supervision circuit allows to monitor this clock and provides a fallback
solution, should the clock be non-functional (missing). A too fast running NTUx cannot be detected.
RTIUC0 is utilized to monitor the NTUx signal. A detection window can be programmed in which a valid
NTU clock pulse needs to occur. If no pulse is detected, the RTI automatically switches back to clock the
Free Running Counter 0 with RTIUC0. In order to avoid a big jitter in the operating ticks, in case a switch
back to RTIUC0 happens, RTICPUC0 should be set to a value so the clock frequency RTIUC0 outputs is
approximately the same as the NTUx frequency.