TC1796
System Units (Vol. 1 of 2)
System Control Unit
User’s Manual
5-9
V2.0, 2007-07
SCU, V2.0
5.3
External Request Unit (ERU)
In many cases, external events are used to trigger actions inside a microcontroller. This
can be done by triggering external interrupts, which are then serviced by the CPU.
Another possibility is to activate module functions that are related to external signals,
such as the start of analog-to-digital conversions, counting control for a timer unit or to
start a DMA transfer.
Due to the large variety of possible conditions of external signals, the simple generation
of interrupt events after the detection of edges of the external signals might not be
enough. Therefore, it can become necessary to check for patterns (gating of functions)
or to reroute trigger events from one block to another.
In the TC1796, a flexible External Request Unit (ERU) makes it possible to generate
trigger events that are able to generate interrupts, trigger a DMA transfers, or start
analog-to-digital conversions.
Features
•
Edge-detection of an input signal (rising, falling, or both edges)
•
Event generation with combined conditions of input signals
•
Pattern detection of input pins (e.g gating functionality)
•
Flexible input signal selection
•
Generation of multiple output trigger events possible
The block diagram of the ERU is shown in
Figure 5-1
External Request Unit Block Diagram
External
Request
Inputs
MCB05613
External Request
Selection Unit
(ERS)
External Trigger
Logic Unit
(ETL)
Interrupt Gating
Logic Unit
(INTG)
Output
Channel 0
Output
Channel 1
Output
Channel 3
Output
Channel 2
External Request Unit (ERU)
External
Request
Outputs
4
Input Channel 0
Input Channel 1
Input Channel 2
Input Channel 3
4
4
4
