diff --git a/avr/modules/uart_hw2/comonuart1.asm b/avr/modules/uart_hw2/comonuart1.asm
index f93b950..3cba555 100644
--- a/avr/modules/uart_hw2/comonuart1.asm
+++ b/avr/modules/uart_hw2/comonuart1.asm
@@ -149,6 +149,22 @@ comOnUart1StartReading:
 ; @clobbers R16, R17, X, Z (R22, R24, R25)
 
 comOnUart1StartWriting:
+  push r15
+    inr r15, SREG
+    cli
+    rcall comOnUart1StartWriting_noIrq
+    brcc comOnUart1StartWriting_clc
+    outr SREG, r15
+  pop r15
+  sec
+  ret
+comOnUart1StartWriting_clc:
+    outr SREG, r15
+  pop r15
+  clc
+  ret
+
+comOnUart1StartWriting_noIrq:
   rcall comOnUart1AcquireAttn                ; (R22)
   brcc comOnUart1StartWriting_ebusy
   ; copy buffer
@@ -451,7 +467,7 @@ comOnUart1StartTx:
   cbr r16, (1<<TXC1)                             ; clear TXCn interrupt
   outr UCSR1A, r16
   inr r16, UCSR1B
-  sbr r16, (1<<UDRIE1) | (1<<TXC1) | (1<<TXEN1)  ; enable TX UDRE and TXC1 interrupt, enable transceive
+  sbr r16, (1<<UDRIE1) | (1<<TXCIE1) | (1<<TXEN1)  ; enable TX UDRE and TXC1 interrupt, enable transceive
   outr UCSR1B, r16
   ret
 ; @end
@@ -465,7 +481,7 @@ comOnUart1StartTx:
 
 comOnUart1StopTx:
   inr r16, UCSR1B
-  cbr r16, (1<<UDRIE1) | (1<<TXC1) | (1<<TXEN1)  ; disable TX UDRE and TXC1 interrupt, enable transceive
+  cbr r16, (1<<UDRIE1) | (1<<TXCIE1) | (1<<TXEN1)  ; disable TX UDRE and TXC1 interrupt, enable transceive
   outr UCSR1B, r16
   ret
 ; @end
@@ -806,7 +822,7 @@ comOnUart1TxUdreIsr_end:
 comOnUart1TxCharIsr:
   ; disable further TXC interrupts
   inr r16, UCSR1B
-  cbr r16, (1<<TXC1)                          ; disable TXC1 interrupt
+  cbr r16, (1<<TXCIE1)                        ; disable TXC1 interrupt
   outr UCSR1B, r16
   rcall comOnUart1StopTx                      ; (R16)
   ldi r16, UART_HW2_MODE_MSGSENT