From 7f0a89cc4a4e079c4c5889d45f28d6d84864c8b3 Mon Sep 17 00:00:00 2001
From: Uri Shaked
Date: Sat, 17 Jul 2021 17:55:24 +0300
Subject: feat(usart): add `immediate` parameter to writeByte()

The value will be available immediately to the user program instead of waiting one symbol time before making it available.
---
 src/peripherals/usart.ts | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

(limited to 'src/peripherals/usart.ts')

diff --git a/src/peripherals/usart.ts b/src/peripherals/usart.ts
index 81451ba..1b7546b 100644
--- a/src/peripherals/usart.ts
+++ b/src/peripherals/usart.ts
@@ -193,19 +193,23 @@ export class AVRUSART {
     return this.rxBusyValue;
   }
 
-  writeByte(value: number) {
-    const { cpu, config } = this;
-    if (this.rxBusyValue || !(cpu.data[config.UCSRB] & UCSRB_RXEN)) {
+  writeByte(value: number, immediate = false) {
+    const { cpu } = this;
+    if (this.rxBusyValue || !this.rxEnable) {
       return false;
     }
-    this.rxBusyValue = true;
-    cpu.addClockEvent(() => {
+    if (immediate) {
       this.rxByte = value;
-      this.rxBusyValue = false;
       cpu.setInterruptFlag(this.RXC);
       this.onRxComplete?.();
-    }, this.cyclesPerChar);
-    return true;
+    } else {
+      this.rxBusyValue = true;
+      cpu.addClockEvent(() => {
+        this.rxBusyValue = false;
+        this.writeByte(value, true);
+      }, this.cyclesPerChar);
+      return true;
+    }
   }
 
   private get cyclesPerChar() {
-- 
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