diff --git a/bacnet-stack/ports/pic18f6720/BACnet-Server.mcp b/bacnet-stack/ports/pic18f6720/BACnet-Server.mcp
index 444b2bd7..b4932d36 100644
--- a/bacnet-stack/ports/pic18f6720/BACnet-Server.mcp
+++ b/bacnet-stack/ports/pic18f6720/BACnet-Server.mcp
@@ -83,6 +83,7 @@ file_056=.
 file_057=.
 file_058=.
 file_059=.
+file_060=.
 [GENERATED_FILES]
 file_000=no
 file_001=no
@@ -144,6 +145,7 @@ file_056=no
 file_057=no
 file_058=no
 file_059=no
+file_060=no
 [OTHER_FILES]
 file_000=no
 file_001=no
@@ -205,6 +207,7 @@ file_056=no
 file_057=no
 file_058=no
 file_059=no
+file_060=no
 [FILE_INFO]
 file_000=C:\code\bacnet-stack\src\abort.c
 file_001=C:\code\bacnet-stack\src\bacapp.c
@@ -244,28 +247,29 @@ file_034=C:\code\bacnet-stack\src\npdu.c
 file_035=C:\code\bacnet-stack\src\version.c
 file_036=apdu.c
 file_037=C:\code\bacnet-stack\demo\handler\noserv.c
-file_038=stdbool.h
-file_039=stdint.h
-file_040=rs485.h
-file_041=mstp.h
-file_042=C:\mcc18\h\p18f6720.h
-file_043=C:\code\bacnet-stack\include\bits.h
-file_044=C:\code\bacnet-stack\include\abort.h
-file_045=C:\code\bacnet-stack\include\ai.h
-file_046=C:\code\bacnet-stack\include\apdu.h
-file_047=C:\code\bacnet-stack\include\bacaddr.h
-file_048=C:\code\bacnet-stack\include\bacapp.h
-file_049=C:\code\bacnet-stack\include\bacdcode.h
-file_050=C:\code\bacnet-stack\include\bacdef.h
-file_051=C:\code\bacnet-stack\include\bacenum.h
-file_052=C:\code\bacnet-stack\include\bacerror.h
-file_053=C:\code\bacnet-stack\include\bacint.h
-file_054=C:\code\bacnet-stack\include\bacprop.h
-file_055=C:\code\bacnet-stack\include\bacreal.h
-file_056=C:\code\bacnet-stack\include\bacstr.h
-file_057=C:\code\bacnet-stack\include\bigend.h
-file_058=C:\code\bacnet-stack\include\config.h
-file_059=18F6720.lkr
+file_038=C:\code\bacnet-stack\src\fifo.c
+file_039=stdbool.h
+file_040=stdint.h
+file_041=rs485.h
+file_042=mstp.h
+file_043=C:\mcc18\h\p18f6720.h
+file_044=C:\code\bacnet-stack\include\bits.h
+file_045=C:\code\bacnet-stack\include\abort.h
+file_046=C:\code\bacnet-stack\include\ai.h
+file_047=C:\code\bacnet-stack\include\apdu.h
+file_048=C:\code\bacnet-stack\include\bacaddr.h
+file_049=C:\code\bacnet-stack\include\bacapp.h
+file_050=C:\code\bacnet-stack\include\bacdcode.h
+file_051=C:\code\bacnet-stack\include\bacdef.h
+file_052=C:\code\bacnet-stack\include\bacenum.h
+file_053=C:\code\bacnet-stack\include\bacerror.h
+file_054=C:\code\bacnet-stack\include\bacint.h
+file_055=C:\code\bacnet-stack\include\bacprop.h
+file_056=C:\code\bacnet-stack\include\bacreal.h
+file_057=C:\code\bacnet-stack\include\bacstr.h
+file_058=C:\code\bacnet-stack\include\bigend.h
+file_059=C:\code\bacnet-stack\include\config.h
+file_060=18F6720.lkr
 [SUITE_INFO]
 suite_guid={5B7D72DD-9861-47BD-9F60-2BE967BF8416}
 suite_state=
diff --git a/bacnet-stack/ports/pic18f6720/BACnet-Server.mcw b/bacnet-stack/ports/pic18f6720/BACnet-Server.mcw
index 31711b56..679e31fb 100644
Binary files a/bacnet-stack/ports/pic18f6720/BACnet-Server.mcw and b/bacnet-stack/ports/pic18f6720/BACnet-Server.mcw differ
diff --git a/bacnet-stack/ports/pic18f6720/rs485.c b/bacnet-stack/ports/pic18f6720/rs485.c
index 646833d1..b34ea97a 100644
--- a/bacnet-stack/ports/pic18f6720/rs485.c
+++ b/bacnet-stack/ports/pic18f6720/rs485.c
@@ -41,14 +41,15 @@ extern volatile struct mstp_port_struct_t MSTP_Port;
 /* the baud rate is adjustable */
 uint32_t RS485_Baud_Rate = 38400;
 
-/*#pragma udata MSTPPortData
- */
+/* the FIFO structures for sending and receiving */
+FIFO_BUFFER FIFO_Rx;
+FIFO_BUFFER FIFO_Tx;
+#pragma udata MSTPPortData
 /* the buffer for receiving data (size must be a power of 2) */
 volatile uint8_t RS485_Rx_Buffer[128];
-FIFO_BUFFER FIFO_Rx;
 /* the buffer for sending data (size must be a power of 2) */
 volatile uint8_t RS485_Tx_Buffer[128];
-FIFO_BUFFER FIFO_Tx;
+#pragma udata
 
 /****************************************************************************
 * DESCRIPTION: Transmits a frame using the UART
@@ -67,7 +68,7 @@ void RS485_Send_Frame(
     if (!buffer)
         return;
 
-    while (!Empty(&FIFO_Tx)) {
+    while (!FIFO_Empty(&FIFO_Tx)) {
         /* buffer is not empty.  Wait for ISR to transmit. */
     };
 
@@ -83,18 +84,19 @@ void RS485_Send_Frame(
         /* The line has not been silent long enough, so wait. */
     };
 
-    FIFO_Add(&FIFO_Tx, buffer, nbytes);
-    /* disable the receiver */
-    PIE3bits.RC2IE = 0;
-    RCSTA2bits.CREN = 0;
-    /* enable the transceiver */
-    RS485_TX_ENABLE = 1;
-    RS485_RX_DISABLE = 1;
-    /* enable the transmitter */
-    TXSTA2bits.TXEN = 1;
-    PIE3bits.TX2IE = 1;
-    /* reset the silence timer per MSTP spec, sort of */
-    mstp_port->SilenceTimer = 0;
+    if (FIFO_Add(&FIFO_Tx, buffer, nbytes)) {
+        /* disable the receiver */
+        PIE3bits.RC2IE = 0;
+        RCSTA2bits.CREN = 0;
+        /* enable the transceiver */
+        RS485_TX_ENABLE = 1;
+        RS485_RX_DISABLE = 1;
+        /* enable the transmitter */
+        TXSTA2bits.TXEN = 1;
+        PIE3bits.TX2IE = 1;
+        /* reset the silence timer per MSTP spec, sort of */
+        mstp_port->SilenceTimer = 0;
+    }
 
     return;
 }
diff --git a/bacnet-stack/src/fifo.c b/bacnet-stack/src/fifo.c
index 3e3e216b..df6170ae 100755
--- a/bacnet-stack/src/fifo.c
+++ b/bacnet-stack/src/fifo.c
@@ -164,8 +164,9 @@ bool FIFO_Add(
     /* limit the ring to prevent overwriting */
     if (FIFO_Available (b, count)) {
         while (count) {
-            b->buffer[b->head % b->buffer_len] = data_byte;
+            b->buffer[b->head % b->buffer_len] = *data_bytes;
             b->head++;
+            data_bytes++;
             count--;
         }
         status = true;