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timer.go
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timer.go
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// This file is part of Gopher2600.
//
// Gopher2600 is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Gopher2600 is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Gopher2600. If not, see <https://www.gnu.org/licenses/>.
package peripherals
import (
"github.com/jetsetilly/gopher2600/hardware/memory/cartridge/arm/architecture"
)
// Timer implements a simple timer as used in the LCP2000.
type Timer struct {
mmap architecture.Map
enabled bool
control uint32
counter uint32
}
func NewTimer(mmap architecture.Map) Timer {
return Timer{
mmap: mmap,
}
}
func (t *Timer) Reset() {
t.counter = 0
}
// stepping of timer assumes an APB divider value of one.
func (t *Timer) Step(cycles uint32) {
if !t.enabled {
return
}
t.counter += cycles
}
func (t *Timer) Write(addr uint32, val uint32) bool {
switch addr {
case t.mmap.TIMERcontrol:
t.enabled = val&0x01 == 0x01
t.control = val
case t.mmap.TIMERvalue:
t.counter = val
default:
return false
}
return true
}
func (t *Timer) Read(addr uint32) (uint32, bool) {
var val uint32
switch addr {
case t.mmap.TIMERcontrol:
val = t.control
case t.mmap.TIMERvalue:
val = t.counter
default:
return 0, false
}
return val, true
}