====== Timers ======

The gamepad has the following timer registers: (TODO word better)
^ Address    ^ Desc. ^
| 0xF0000400 | Prescaler for timer 0/1 |
| 0xF0000404 | Prescaler for count-up timer |
| 0xF0000408 | Count-up timer |
| 0xF0000410 | Timer 0 control |
| 0xF0000414 | Timer 0 counter |
| 0xF0000418 | Timer 0 target  |
| 0xF0000420 | Timer 1 control |
| 0xF0000424 | Timer 1 counter |
| 0xF0000428 | Timer 1 target  |


===== Prescalers =====

Registers 0xF0000400 and 0xF0000404 control the rate at which timers 0/1 and the count-up timer run, respectively.

They are simple prescaler counters. For example, setting them to 63 will divide the input clock by 64.

These registers are 8 bits wide.

===== Count-up timer =====

This is a simple timer that is always counting up. When writing a value to 0xF0000408, it will begin counting from the new value.

This register is 32 bits wide.


===== Timer 0 =====

**0xF0000410**

Timer control.

^ Bits ^ Desc. ^
| 0    | ?? |
| 1    | Timer enable |
| 2    | Count direction; 0=up, 1=down |
| 4-6  | Prescaler |

Bit0 is possibly used by firmware code but has no observable effect.

Writing 0 to bit1 resets the timer to 0.

The prescaler value has the following possible settings:
^ Value ^ Frequency ^
| 0     | Divide by 2 |
| 1     | Divide by 4 |
| 2     | Divide by 8 |
| 3     | Divide by 16 |
| 4     | Divide by 32 |
| 5     | Divide by 64 |
| 6     | Divide by 128 |
| 7     | Divide by 256 |


**0xF0000414**

Counter. Can be written to, the timer will count from the new value. Writes are ignored when the timer isn't active.

When the timer goes past the target in count-up mode, or below zero in count-down mode, the timer is reloaded (to 0 in count-up mode, to the target value in count-down mode) and IRQ 0x00 is triggered.

Writing a new value greater than the target does not cause a reload.

This register is 32 bits wide.


**0xF0000418**

Target.

In count-up mode, before a reload, the last value the timer takes is equal to the target. It is then reloaded to 0.

In count-down mode, before a reload, the last value the timer takes is 0. It is then reloaded to the target value.


===== Timer 1 =====

Function identical to timer 0, except it triggers IRQ 0x01.