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Hardware Timer

The hardware timer is designed so that programs can asyncronously schedule timers that will emit an interrupt upon completion. This can be used to avoid repeatedly polling UPTMS or for situations where this isn’t possible like interrupting running code after a certain amount of time (which allows for task switching mechanisms).

Protocol

Section titled “Protocol”

The hardware timer is a command based device which means you start by sending it a number representing what you’d like to you, then a number of arguments.

Command ID
New Timer 1

New Timer

Section titled “New Timer”

Send a value for the duration of the timer in milliseconds, and then a timer ID. Once the time elapses the timer will emit an interrupt with code 0x71, and the next value it will emit from the serial protocol will be the timer ID provided upon creation.

For example to create a timer for 10ms do:

OUT 0x03, 0x01     ; New Timer
OUT 0x03, 10       ; 10ms
OUT 0x03, 5        ; Timer ID of 5
; Timer is now set