command table 最多有几层

问题现象
在CMD命令表中定义了四层 如下

Table MAIN = { /*
--------------------------------------
# subtable class options command word
- --------- ---------- -------------------- ----------------- */
{ 1, ISOMMANAGER, INHERIT, NONE | CMDSTR (CMDID_ISOMMANAGER), "ISOMMANAGER" },
};

Table ISOMMANAGER = { /*
--------------------------------------
# subtable class options command word
- --------- --------- ----------------- ---------- */
{ 1, ZERO , INHERIT, NONE | CMDSTR (CMDID_ISOMMANAGER), "START" },
{ 2, SELECT , INHERIT, NONE | CMDSTR (CMDID_ISOMMANAGER), "SELECT" },

};

Table SELECT = { /*
--------------------------------------
# subtable class options command word
- --------- --------- ----------------- ---------- */
{ 30, ZERO, INHERIT, NONE | CMDSTR (CMDID_ISOMMANAGER), "OPEN" },
{ 31, ZERO, INHERIT, NONE | CMDSTR (CMDID_ISOMMANAGER_SELECT), "OK" },
{ 40, ROUTE, INHERIT, NONE | CMDSTR (CMDID_ISOMMANAGER_ROUTE), "ROUTE" },

};

Table ROUTE = { /*
--------------------------------------
# subtable class options command word
- --------- --------- ----------------- ---------- */
{ 41, ZERO , INHERIT, NONE | CMDSTR (CMDID_ISOMMANAGER_ROUTE), "DIRECTION" },
{ 42, ZERO , INHERIT, NONE | CMDSTR (CMDID_ISOMMANAGER_ROUTE), "RESET" },

};

但是 调用 ISOMMANAGER SELECT ROUTE RESET 的时候就说在这个AP中没有定义。但是如果改为三层，就可以调用。

想请教一下，这个MS中是不是对CMD有层数的制限。