+-------------------------------+<-+
| Byte containing octal value 1 |   \
+-------------------------------+    +  
| Byte containing octal value 0 |    |
+-------------------------------+    |
|   Low-order byte of length    |    |
+-------------------------------+    +-- Length
|   High-order byte of length   |    |
+-------------------------------+    |
|                               |    |
|         Data bytes            |    +
|                               |   /
+-------------------------------+<-+
|        Checksum byte          |
+-------------------------------+