Fix TCNT0 write behavior

tiberiusbrown · Mar 15, 2024 · 38f0586 · 38f0586
1 parent 9c3b8eb
commit 38f0586
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Showing 3 changed files with 10 additions and 0 deletions.
diff --git a/src/absim.hpp b/src/absim.hpp
@@ -325,6 +325,7 @@ struct atmega32u4_t
     timer8_t timer0;
     static void timer0_handle_st_regs(atmega32u4_t& cpu, uint16_t ptr, uint8_t x);
     static void timer0_handle_st_tifr(atmega32u4_t& cpu, uint16_t ptr, uint8_t x);
+    static void timer0_handle_st_tcnt(atmega32u4_t& cpu, uint16_t ptr, uint8_t x);
     static uint8_t timer0_handle_ld_tcnt(atmega32u4_t& cpu, uint16_t ptr);
     void update_timer0();
 

diff --git a/src/absim_reset.cpp b/src/absim_reset.cpp
@@ -66,6 +66,7 @@ void atmega32u4_t::reset()
 
     for(int i = 0x44; i <= 0x48; ++i)
         st_handlers[i] = timer0_handle_st_regs;
+    st_handlers[0x46] = timer0_handle_st_tcnt;
     for(int i = 0x80; i <= 0x8d; ++i)
         st_handlers[i] = timer1_handle_st_regs;
     for(int i = 0x90; i <= 0x9d; ++i)

diff --git a/src/absim_timer.hpp b/src/absim_timer.hpp
@@ -843,6 +843,14 @@ uint8_t atmega32u4_t::timer0_handle_ld_tcnt(atmega32u4_t& cpu, uint16_t ptr)
     return cpu.data[ptr];
 }
 
+void atmega32u4_t::timer0_handle_st_tcnt(atmega32u4_t& cpu, uint16_t ptr, uint8_t x)
+{
+    cpu.update_timer0();
+    cpu.data[ptr] = x;
+    cpu.timer0.tcnt = x;
+    cpu.update_timer0();
+}
+
 ARDENS_FORCEINLINE void atmega32u4_t::update_timer1()
 {
     update_timer16(*this, timer1);