差错报文

     <ERR> <Code> <Command length> <Command in error>

<Code> 是一个八位字段，用于指明差错类型。已分配的代码如下所示。<Command length> 是一个 16 位整数，表示 <Command in error> 的长度，以位为单位。<Command in error> 就是非法命令。

<Code> 的取值范围如下所示，采用十六进制表示。

     00     Unspecified error types
     10-0F  Resource errors
     10-1F  Status errors
     20-2F  Content errors
     30-3F  Unused

<Code> 的具体取值及其含义如下所示。

     <Code> value   Semantics

         00         Unspecified errors.
         01         Request for an invalid resource.
         02         Request for an exhausted resource, try later.
        03-0F       Unused.
         10         Invalid <RSM>, i.e., link connected but unblocked.
         11         Invalid <SPD>.
         12         Invalid <ASG>, i.e., connected but no <RDY>
                      received.

     <Code> value   Semantics

         13         Message received on blocked link.
        14-1F       Unused.
         20         Unknown command code.
         21         Message received on unconnected link.
         22         Invalid <RFC>.
         23         Invalid <CLS>.
         24         Invalid <RSM>, i.e., link not connected.
         25         Invalid <FND>.
         26         Invalid <END>.
         27         Invalid <RDY>.
         28         Invalid <ASG>, i.e., not connected.
        29-2F       Unused.
        30-FF       Unused.