Hom/Sam Change Outside Of Reset - Texas Instruments OMAP5910 Technical Reference Manual

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MPU Interface

HOM/SAM Change Outside of Reset

ST3—HOM_P Bit (Bit 8)

the same memory at the same time, priority is given to the DSP controllers. The

MPU domain access in SAM is synchronized to the internal DSP CPU clock,

which can add access latency for the MPU transfers.

HOM provides the MPU with exclusive access to the DSP SARAM or public

peripherals, primarily to support high-speed transfers from to DSP during DSP

reset or IDLE conditions. During DSP reset condition, HOM_M and HOM_P

are invoked. In HOM_M the MPUI interface does not have access to the

DARAM (0x000000 – 0x00FFFF), but it has access to all the SARAM

(0x010000– 0x050000). The MPU must configure the MPUI_DSP_MPUI

CONFIG register to specify which blocks of SARAM are accessible in HOM

prior to access, because the reset default is for no SARAM access during

An additional condition is that in HOM_P only the MPU can access the DSP

peripheral bus.

Only the DSP can invoke a HOM/SAM change outside of reset. The mode

change is initiated by a DSP write to HOM_P bit (bit 8) and HOM_R bit (bit 9)

of the ST3 register. The appropriate bit is written to request the SAM_M/

HOM_M or SAM_P/HOM_P change. The mode change is not reflected on bits

8 and 9 in ST3 until the internal controller has actually completed the mode

switch. Therefore, the DSP polls bits 8 and 9 after requesting a mode change

to ensure the mode change is complete.

The HOM_M/SAM_M and HOM_R/SAM_R status can be observed by the

MPU by reading the MPU_DSP_Status_Register (see Section 2.9, MPU

Interface, for details).

The host-only mode for peripherals (HOM_P) bit determines whether the

peripherals are owned only by the MPU or shared by the MPU and the DSP:

Peripherals are shared by the MPU and the DSP. If you clear the HOM_P

bit, a request for sharing is sent to the peripheral domain controller. If the

peripheral domain controller clears the HOM_P bit, the clearing indicates

that the MPU no longer has exclusive ownership of the peripherals.

Peripherals are owned only by the MPU. If you set the HOM_P bit, a

request for HOM is sent to the peripheral domain controller. If the peripher-

al domain controller sets the HOM_P bit, the setting indicates that the

MPU has exclusive ownership of the peripherals.