TIMER0¶

Timer¶

Provides a generic Timer core.

The Timer is implemented as a countdown timer that can be used in various modes:

• Polling : Returns current countdown value to software

• One-Shot: Loads itself and stops when value reaches 0

• Periodic: (Re-)Loads itself when value reaches 0

en register allows the user to enable/disable the Timer. When the Timer is enabled, it is automatically loaded with the value of load register.

When the Timer reaches 0, it is automatically reloaded with value of reload register.

The user can latch the current countdown value by writing to update_value register, it will update value register with current countdown value.

To use the Timer in One-Shot mode, the user needs to:

• Disable the timer

• Set the load register to the expected duration

• (Re-)Enable the Timer

To use the Timer in Periodic mode, the user needs to:

• Disable the Timer

• Set the load register to 0

• Set the reload register to the expected period

• Enable the Timer

For both modes, the CPU can be advertised by an IRQ that the duration/period has elapsed. (The CPU can also do software polling with update_value and value to know the elapsed duration)

Register Listing for TIMER0¶

TIMER0_LOAD¶

Address: 0xf0008800 + 0x0 = 0xf0008800

Load value when Timer is (re-)enabled. In One-Shot mode, the value written to this register specifies the Timer’s duration in clock cycles.

TIMER0_RELOAD¶

Address: 0xf0008800 + 0x4 = 0xf0008804

Reload value when Timer reaches 0. In Periodic mode, the value written to this register specify the Timer’s period in clock cycles.

TIMER0_EN¶

Address: 0xf0008800 + 0x8 = 0xf0008808

Enable flag of the Timer. Set this flag to 1 to enable/start the Timer. Set to 0 to disable the Timer.

TIMER0_UPDATE_VALUE¶

Address: 0xf0008800 + 0xc = 0xf000880c

Update trigger for the current countdown value. A write to this register latches the current countdown value to value register.

TIMER0_VALUE¶

Address: 0xf0008800 + 0x10 = 0xf0008810

Latched countdown value. This value is updated by writing to update_value.

TIMER0_EV_STATUS¶

Address: 0xf0008800 + 0x14 = 0xf0008814

This register contains the current raw level of the zero event trigger. Writes to this register have no effect.

TIMER0_EV_PENDING¶

Address: 0xf0008800 + 0x18 = 0xf0008818

When a zero event occurs, the corresponding bit will be set in this register. To clear the Event, set the corresponding bit in this register.

TIMER0_EV_ENABLE¶

Address: 0xf0008800 + 0x1c = 0xf000881c

This register enables the corresponding zero events. Write a 0 to this register to disable individual events.