diff --git a/devices/floppy/swim3.cpp b/devices/floppy/swim3.cpp
index cdf9cd9..39c38c6 100644
--- a/devices/floppy/swim3.cpp
+++ b/devices/floppy/swim3.cpp
@@ -80,6 +80,8 @@ uint8_t Swim3Ctrl::read(uint8_t reg_offset)
     uint8_t status_addr, rddata_val, old_int_flags, old_error;
 
     switch(reg_offset) {
+    case Swim3Reg::Timer:
+        return this->calc_timer_val();
     case Swim3Reg::Error:
         old_error = this->error;
         this->error = 0;
@@ -127,7 +129,7 @@ void Swim3Ctrl::write(uint8_t reg_offset, uint8_t value)
 
     switch(reg_offset) {
     case Swim3Reg::Timer:
-        LOG_F(INFO, "SWIM3: writing %d to the Timer register", value);
+        this->init_timer(value);
         break;
     case Swim3Reg::Param_Data:
         this->pram = value;
@@ -357,6 +359,44 @@ void Swim3Ctrl::stop_disk_access()
     this->access_timer_id = 0;
 }
 
+void Swim3Ctrl::init_timer(const uint8_t start_val)
+{
+    if (this->timer_val) {
+        LOG_F(WARNING, "SWIM3: attempt to re-arm the timer");
+    }
+    this->timer_val = start_val;
+    if (!this->timer_val) {
+        this->one_us_timer_start = 0;
+        return;
+    }
+
+    this->one_us_timer_start = TimerManager::get_instance()->current_time_ns();
+
+    this->one_us_timer_id = TimerManager::get_instance()->add_oneshot_timer(
+        this->timer_val * NS_PER_USEC,
+        [this]() {
+            this->timer_val = 0;
+            this->int_flags |= INT_TIMER_DONE;
+            update_irq();
+        }
+    );
+}
+
+uint8_t Swim3Ctrl::calc_timer_val()
+{
+    if (!this->timer_val) {
+        return 0;
+    }
+
+    uint64_t time_now   = TimerManager::get_instance()->current_time_ns();
+    uint64_t us_elapsed = (time_now - this->one_us_timer_start) / NS_PER_USEC;
+    if (us_elapsed > this->timer_val) {
+        return 0;
+    } else {
+        return (this->timer_val - us_elapsed) & 0xFFU;
+    }
+}
+
 // floppy disk formats properties for the cases
 // where disk format needs to be specified manually
 static const std::vector<std::string> FloppyFormats = {
diff --git a/devices/floppy/swim3.h b/devices/floppy/swim3.h
index ed235a4..156dfb6 100644
--- a/devices/floppy/swim3.h
+++ b/devices/floppy/swim3.h
@@ -64,9 +64,10 @@ enum {
 
 /** Interrupt flags. */
 enum {
-    INT_STEP_DONE = 0x02,
-    INT_ID_READ   = 0x04,
-    INT_SECT_DONE = 0x08,
+    INT_TIMER_DONE = 0x01,
+    INT_STEP_DONE  = 0x02,
+    INT_ID_READ    = 0x04,
+    INT_SECT_DONE  = 0x08,
 };
 
 // SWIM3 internal states.
@@ -96,19 +97,22 @@ public:
     };
 
 protected:
-    void update_irq();
-    void start_stepping();
-    void do_step();
-    void stop_stepping();
-    void start_disk_access();
-    void disk_access();
-    void stop_disk_access();
+    void    update_irq();
+    void    start_stepping();
+    void    do_step();
+    void    stop_stepping();
+    void    start_disk_access();
+    void    disk_access();
+    void    stop_disk_access();
+    void    init_timer(const uint8_t start_val);
+    uint8_t calc_timer_val();
 
 private:
     std::unique_ptr<MacSuperdrive::MacSuperDrive> int_drive;
 
     DmaBidirChannel*    dma_ch;
 
+    uint8_t timer_val = 0; // internal timer that decrements at a 1 us rate
     uint8_t setup_reg;
     uint8_t mode_reg;
     uint8_t error;
@@ -128,9 +132,12 @@ private:
     uint8_t rd_line;
     int     cur_state;
 
+    int     one_us_timer_id = 0;
     int     step_timer_id   = 0;
     int     access_timer_id = 0;
 
+    uint64_t    one_us_timer_start = 0;
+
     // Interrupt related stuff
     InterruptCtrl* int_ctrl = nullptr;
     uint32_t       irq_id   = 0;