TI中文支持网最新的文档里的External Peripheral Interface (EPI)章节中新添加了19.9 C28x Access to EPI。说明c28可以直接访问epi。阅读章节以后产生了以下几个疑问。
1、首先，文档中说明，This means that M3 software must configure the EPI in a particular mode before C28x software can access the external device via EPI.（P 1388)所以需要先在M3中对epi进行配置。对于之后DSP与EPI如何交换信息就没有再提了。
2、RTW的作用是否只是起到阻塞的作用，而且RTW只是存在于M3 与 C28都需要访问epi的时候需要使用 。因为文档中有提到 Once EPI is grabbed by C28x software (GRAB = 1), all accesses to EPI from M3/uDMA will be stalled until EPI is released (GRAB = 0) by C28x software.The RTW feature is only needed in an application where both subsystems (master and control) are accessing EPI and one needs to provide a window for dedicated access to EPI from the control (C28x) subsystem. Otherwise, by default, both subsystems have access to EPI with round-robin arbitration.
3、所以，假如只需要DSP和EPI到底是要如何才能直接交换数据的呢？
dajun zhao：
C28核控制的最大地址是A17,那更高地址怎么办啊?
