以下是3GPP协议的文档，里面有几个细节难以翻译，翻译出来总觉得前后自相矛盾，红色部分是我的最大盲点。请哥们不要用百度、谷歌这些在线翻译，小哥我不是不认识单词。
Table 4.8.3.1: HDLC parameters for address assignment and device scan
PI
| PL
| Description of PV
| 1
| 0 to 19
| Unique ID
| 2
| 1
| HDLC Address
| 3
| 0 to 19
| Bit Mask (for Unique ID), indicates a device scan
| 4
| 1
| Device Type (see table 4.7.1)
| 6
| 2
| Vendor Code as given in AISG v2.0 [4]
|
The device scan messages may be utilised by the primary to identify all secondary stations in the NoAddress state on an interface .
A device scan XID command shall only contain PI=1 (Unique ID) and PI=3 (Bit Mask), see table 4.8.3.1. PI=1 and PI=3 shall be of equal length PL octets.
If in the NoAddress state, the secondary device masks the min(PL,2) left-most octets of its own unique ID with the min(PL,2) left-most octets of the bit mask in the XID command and compares the result with the min(PL,2) left-most octets the unique ID supplied in the XID command. If they match, the secondary device masks the max(0,PL-2) right-most octets of its own unique ID with the max(0,PL-2) right-most octets of the bit mask in the XID command and compares the result with the max(0,PL-2) right-most octets of the unique ID supplied in the XID command. If they also match, the secondary device transmits an XID response message with its own identification data in the fields PI=1 (complete unique ID), PI=4 (device type) and PI=6 (vendor code).
For the device scan comparison, the unique ID of the secondary device shall be padded with NUL characters (character code 0x00) between the second and third left-most positions to a length of 19 octets.
The scan command with zero length (PL=0) of the Unique ID (PI=1) and the Bit Mask (PI=3) shall match all secondary devices in the NoAddress state.
Only matching secondary devices in the NoAddress state shall respond to the device scan messages. |
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