6502/CLK
1
0
Fork 0
mirror of https://github.com/TomHarte/CLK.git synced 2025-04-04 13:31:26 +00:00
Code Issues Projects Releases Wiki Activity

Adds reload during event count mode.

Browse Source 
Plus a helpful bit of TODO.
This commit is contained in:
Thomas Harte 2019-11-19 22:24:32 -05:00
parent 72cb3a1cf6
commit 06edeea866
1 changed files with 13 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
Components/68901/MFP68901.cpp
View File

@ -239,6 +239,15 @@ void MFP68901::set_timer_event_input(int channel, bool value) {
// If the edge bit associated with the TAI or TBI input is a one, it will be active high.
decrement_timer(channel, 1);
}
// TODO:
//
// Altering the edge bit while the timer is in the event count mode can produce a count pulse.
// The interrupt channel associated with the input (I3 for I4 for TAI) is allowed to function normally.
// To count transitions reliably, the input must remain in each state (1/O) for a length of time equal
// to four periods of the timer clock.
//
// (the final bit probably explains 13 cycles of the DE to interrupt latency; not sure about the other ~15)
}
void MFP68901::decrement_timer(int timer, int amount) {
@ -251,7 +260,10 @@ void MFP68901::decrement_timer(int timer, int amount) {
case 2: begin_interrupts(Interrupt::TimerC); break;
case 3: begin_interrupts(Interrupt::TimerD); break;
}
if(timers_[timer].mode == TimerMode::Delay) {
// Re: reloading when in event counting mode; I found the data sheet thoroughly unclear on
// this, but it appears empirically to be correct. See e.g. Pompey Pirates menu 27.
if(timers_[timer].mode == TimerMode::Delay || timers_[timer].mode == TimerMode::EventCount) {
timers_[timer].value += timers_[timer].reload_value; // TODO: properly.
}
}