Output compare

Structure of Microcontroller EA, RST, ALE, PSEN ROM COUNTER INPUTS OSC INTERRUPT CONTROL 4 I/O PORTS BUS CONTROL SERIAL PORT EXTERNAL INTERRUPTS CPU ON - CHIP RAM ETC TIMER 0 TIMER 1 ADDRESS/DATA TXD RXD P0 P1 P2 P3

What are Interrupts? A hardware event is something that happens in the micro-controller's hardware. An example of an event is the RESET that occurs when pin 9 is set low. Micro-controllers are micro-computers whose architecture has been optimized to respond quickly to external events.

Output Compare Interrupts Output compare interrupts are hardware interrupts that are tied to timer events and this means that they can be used by a micro-controller to enforce the real-time processing of events. The output compare event can also be used to effect specific output pins.

Output Compare Interrupts In particular, you will use the output compare interrupt to build a system that outputs a specified voltage using a pulse-width modulation scheme.

Output Compare Interrupts In the Microcontroller output compare events are tied to a 16-bit hardware register (also called a timer) This register is incremented at a rate that can be specified by the programmer.

Output Compare Interrupts When the value of timer register equals the value stored in another output compare register , then an output compare event occurs and the Microcontroller responds by issuing an output compare interrupt . The counter register cannot be reset or stopped by the user.

Output Compare Interrupts So to generate timing events, we compare the value in timer register against another number that is held in an output compare register . When the value in timer register matches the number in the output compare register, we trigger an output-compare event .

Output Compare Interrupts Output compare events are generated in the micro-controller's hardware. This event will result in a hardware interrupt (also called an output compare interrupt) being generated if the interrupt is enabled

Output Compare Interrupts Enabling the interrupt means that the software pays attention to the interrupt. We enable all interrupts by setting the I bit in the condition code register of the micro-controller. This is bit is usually set in the init() function

IEN0 - Interrupt enable register 0

CMOD - PCA counter mode register (address D9H) bit allocation

CCON - PCA counter control register (address 0D8H) bit description

CCAPMn - PCA modules compare/capture register

PCA IN COMPARE MODE The 16-bit software timer mode is used to trigger interrupt routines, which must occur at periodic intervals. It is setup by setting both the ECOM and MAT bits in the module’s CCAPMn register

PCA IN COMPARE MODE The PCA timer will be compared to the module’s capture registers (CCAPnL and CCAPnH) when a match occurs, an interrupt will occur, if the ECCFn (CCAPMn SFR) bit for the module is set.

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Output compare

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Output compare