diff --git a/src/peripherals/rtc.ts b/src/peripherals/rtc.ts
index f0e264c..6f3481a 100644
--- a/src/peripherals/rtc.ts
+++ b/src/peripherals/rtc.ts
@@ -1,26 +1,68 @@
 import { BasePeripheral, Peripheral } from './peripheral';
 
+const RTC_SETUP0 = 0x04;
+const RTC_SETUP1 = 0x08;
 const RTC_CTRL = 0x0c;
 const IRQ_SETUP_0 = 0x10;
+const RTC_RTC1 = 0x18;
+const RTC_RTC0 = 0x1c;
+
+const RTC_ENABLE_BITS = 0x01;
 const RTC_ACTIVE_BITS = 0x2;
+const RTC_LOAD_BITS = 0x10;
 
 export class RP2040RTC extends BasePeripheral implements Peripheral {
-  running = true;
+  setup0 = 0;
+  setup1 = 0;
+  rtc1 = 0;
+  rtc0 = 0;
+  ctrl = 0;
 
   readUint32(offset: number) {
     switch (offset) {
+      case RTC_SETUP0:
+        return this.setup0;
+      case RTC_SETUP1:
+        return this.setup1;
       case RTC_CTRL:
-        return this.running ? RTC_ACTIVE_BITS : 0;
+        return this.ctrl;
       case IRQ_SETUP_0:
         return 0;
+      case RTC_RTC1:
+        return this.rtc1;
+      case RTC_RTC0:
+        return this.rtc0;
     }
     return super.readUint32(offset);
   }
 
   writeUint32(offset: number, value: number) {
     switch (offset) {
+      case RTC_SETUP0:
+        this.setup0 = value;
+        break;
+      case RTC_SETUP1:
+        this.setup1 = value;
+        break;
       case RTC_CTRL:
-        this.running = value > 0; // TODO consult the datasheet
+        // Though RTC_LOAD_BITS is type SC and should be cleared on next cycle, pico-sdk write
+        // RTC_LOAD_BITS & RTC_ENABLE_BITS seperatly.
+        // https://github.com/raspberrypi/pico-sdk/blob/master/src/rp2_common/hardware_rtc/rtc.c#L76-L80
+        if (value & RTC_LOAD_BITS) {
+          this.ctrl |= RTC_LOAD_BITS;
+        }
+        if (value & RTC_ENABLE_BITS) {
+          this.ctrl |= RTC_ENABLE_BITS;
+          this.ctrl |= RTC_ACTIVE_BITS
+          if (this.ctrl & RTC_LOAD_BITS) {
+            this.rtc1 = this.setup0;
+            this.rtc0 = this.setup1;
+            this.ctrl &= ~RTC_LOAD_BITS;
+          }
+        } else {
+          this.ctrl &= ~RTC_ENABLE_BITS
+          this.ctrl &= ~RTC_ACTIVE_BITS
+        }
         break;
       default:
         super.writeUint32(offset, value);