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

Register	Address
TIMER0_LOAD	0xf0005000
TIMER0_RELOAD	0xf0005004
TIMER0_EN	0xf0005008
TIMER0_UPDATE_VALUE	0xf000500c
TIMER0_VALUE	0xf0005010
TIMER0_EV_STATUS	0xf0005014
TIMER0_EV_PENDING	0xf0005018
TIMER0_EV_ENABLE	0xf000501c

TIMER0_LOAD

Address: 0xf0005000 + 0x0 = 0xf0005000

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: 0xf0005000 + 0x4 = 0xf0005004

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: 0xf0005000 + 0x8 = 0xf0005008

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: 0xf0005000 + 0xc = 0xf000500c

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

TIMER0_VALUE

Address: 0xf0005000 + 0x10 = 0xf0005010

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

TIMER0_EV_STATUS

Address: 0xf0005000 + 0x14 = 0xf0005014

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

Field	Name	Description
[0]	ZERO	Level of the zero event

TIMER0_EV_PENDING

Address: 0xf0005000 + 0x18 = 0xf0005018

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.

Field	Name	Description
[0]	ZERO	1 if a zero event occurred. This Event is triggered on a falling edge.

TIMER0_EV_ENABLE

Address: 0xf0005000 + 0x1c = 0xf000501c

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

Field	Name	Description
[0]	ZERO	Write a 1 to enable the zero Event