Figure 23-1: Timer Block Diagram
Timer
MPU
Register Block
Interrupt and
System Reset Control
Interrupt
Reset
Manager
Clock
Manager
L4 Peripheral Bus (osc1_clk)
Slave Interface
Functional Description of the Timer
The 32-bit timer counts down from a programmed value and generates an interrupt when the count reaches
zero. The timer has an independent clock input connected to the system clock signal or to an external clock
source. †
The timer supports the following modes of operation:
• Free-running mode—decrementing from the maximum value (0xFFFFFFFF). Reloads maximum value
upon reaching zero.
• User-defined count mode—generates a periodic interrupt. Decrements from the user-defined count value
loaded from the timer1 load count register (
timer1loadcount
). Reloads the user-defined count upon
reaching zero.
The initial value for the timer (that is, the value from which it counts down) is loaded into the timer by the
timer1loadcount
register. The following events can cause a timer to load the initial count from the
timer1loadcount
register: †
• Timer is enabled after being reset or disabled
• Timer counts down to 0
Clocks
Table 23-1: Timer Clock Characteristics
This table shows the clock signals and connections associated with the timers.
Notes
System Clock
Timer
—
osc1_clk
OSC1 timer 0
OSC1 timer 1
Timer must be disabled if clock
frequency changes
l4_sp_clk
SP timer 0
SP timer 1
Timer Introduction
Altera Corporation
cv_54023
Functional Description of the Timer
23-2
2013.12.30