TI中文支持网TI工程师：
你好！
我咨询一下，AF_DataRequest这个函数发送数据包时，数据包限制的大小，即Z-stack协议栈中是如何修改无线发送数据包的大小？DMAC_MAX_FRAME_SIZE，这个字段与无线发送数据包的大小有什么关系？
li ming1：
Have you solved the confusing problem?
Susan Yang：
回复 li ming1:
The maximum payload size for an application is based on several factors. The MAC layer provides a constant payload length of 116 (can be changed in f8wConfig.cfg – MAC_MAX_FRAME_SIZE). The NWK layer requires a fixed header size, one size with security and one without security. The APS layer has a required, but variable,header size based on a variety of settings, including the ZigBee Protocol Version, APS frame control settings, etc.
Ultimately, the user does not have to calculate the maximum payload size using the aforementioned factors. The AF module provides an API that allows the user to query the stack for the maximum payload size, or the maximum transport unit (MTU). The user can call the function, “afDataReqMTU” (see “af.h”) which will return the MTU, or maximum payload size.
li ming1：
回复 Susan Yang:
It really help a lot , I have checked the function “uint8 afDataReqMTU( afDataReqMTU_t* fields )” and It rerurn a parameter ‘len’ …Do you mean that the maximum payload size is not a fixed value ? If not , how can i change the maximum payload size?For example,now I want to send 200 Bytes datas by AF_Data_Request one time.which apects should i change ?
li ming1：
回复 Susan Yang:
AF_DataRequest这个函数发送数据包时，数据包限制的大小可以更改吗？psdu
