SPRUIN7C March 2020 – March 2024 TMS320F280021 , TMS320F280021-Q1 , TMS320F280023 , TMS320F280023-Q1 , TMS320F280023C , TMS320F280025 , TMS320F280025-Q1 , TMS320F280025C , TMS320F280025C-Q1
In Mailbox Access Mode, the external host only sees the HIC memory mapped region and not the device resources and peripherals. This memory mapped region of the HIC includes the HIC control, status and data registers.
128 bytes of this region is reserved for HIC control and status registers. The remaining 128 bytes is used as a data/buffer space and is split 64 bytes each as Host to Device (H2D) buffer and Device to Host (D2H) buffer. Note that this distinction between H2D and D2H buffer is only in name. Device and external host can each access the combined H2D and D2H buffers of 128 bytes by configuring the H2DBUF_DEVWREN and D2HBUF_HOSTWREN fields in the HICMODECR register. Figure 13-6 shows the Mailbox Access Mode and the minimum external connections required for this mode.