serial clock @ 8khz

lib/src/processor/memory/mmio/serial.rs

@@ -5,7 +5,7 @@ use std::{
 
 use serde::{Deserialize, Serialize};
 
-use crate::util::get_bit;
+use crate::{constants::CLOCK_SPEED, util::get_bit};
 
 #[derive(Copy, Clone, Serialize, Deserialize, Debug, PartialEq)]
 enum ClockSource {
@@ -58,6 +58,7 @@ struct InputByte {
 }
 
 const BYTE_DELAY: usize = 2000;
+const CLOCK_DIV: usize = CLOCK_SPEED / 8192;
 
 impl InputByte {
     fn advance(&mut self, rx: &Option<Receiver<u8>>) -> u8 {
@@ -104,6 +105,7 @@ pub struct Serial {
     bits_remaining: u8,
     control: SerialControl,
     target: SerialTarget,
+    clock_inc: usize,
 }
 
 #[derive(Serialize, Deserialize)]
@@ -113,6 +115,7 @@ pub struct SerialSaveState {
     input_byte: InputByte,
     bits_remaining: u8,
     control: SerialControl,
+    clock_inc: usize,
 }
 
 impl SerialSaveState {
@@ -123,6 +126,7 @@ impl SerialSaveState {
             input_byte: serial.input_byte,
             bits_remaining: serial.bits_remaining,
             control: serial.control,
+            clock_inc: serial.clock_inc,
         }
     }
 }
@@ -136,6 +140,7 @@ impl Serial {
             bits_remaining: 7,
             control: SerialControl::default(),
             target,
+            clock_inc: 0,
         }
     }
 
@@ -147,6 +152,7 @@ impl Serial {
             bits_remaining: state.bits_remaining,
             control: state.control,
             target,
+            clock_inc: state.clock_inc,
         }
     }
 
@@ -165,6 +171,9 @@ impl Serial {
             &None
         };
         for _ in 0..steps {
+            self.clock_inc += 1;
+            if self.clock_inc >= CLOCK_DIV {
+                self.clock_inc %= CLOCK_DIV;
                 if ime {
                     self.input_byte.input_delay = self.input_byte.input_delay.saturating_sub(1);
                 }
@@ -198,6 +207,7 @@ impl Serial {
                     }
                 }
             }
+        }
         will_interrupt
     }