Texas Instruments TMS320DM646x Power Management, Emulation Considerations, Emulation Control

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Architecture

2.17 Power Management

Each of the three main components of the EMAC peripheral can independently be placed in reduced-power modes to conserve power during periods of low activity. The power management of the EMAC peripheral is controlled by the processor Power and Sleep Controller (PSC). The PSC acts as a master controller for power management on behalf of all of the peripherals on the device.

The power conservation modes available for each of the three components of the EMAC/MDIO peripheral are:

∙Idle/Disabled state. This mode stops the clocks going to the peripheral, and prevents all the register accesses. After reenabling the peripheral from this idle state, all the registers values prior to setting into the disabled state are restored, and data transmission can proceed. No reinitialization is required.

∙Synchronized reset. This state is similar to the Power-on Reset (POR) state, when the processor is turned-on; reset to the peripheral is asserted, and clocks to the peripheral are gated after that. The registers are reset to their default value. When powering-up after a synchronized reset, all the EMAC submodules need to be reinitialized before any data transmission can happen.

For more information on the use of the processor Power and Sleep Controller (PSC), see the TMS320DM646x DMSoC ARM Subsystem Reference Guide (SPRUEP9).

2.18 Emulation Considerations

Note: For correct operation, the EMAC and EMAC control module must both be suspended.

Thus, the EMCONTROL and CMEMCONTROL registers must be configured alike.

EMAC emulation control is implemented for compatibility with other peripherals. The SOFT and FREE bits in the emulation control register (EMCONTROL) allow EMAC operation to be suspended. Additionally, emulation control is also implemented in the EMAC control module with the EMAC control module emulation control register (CMEMCONTROL) to allow the EMAC control module activity to be suspended.

When the emulation suspend state is entered, the EMAC stops processing receive and transmit frames at the next frame boundary. Any frame currently in reception or transmission is completed normally without suspension. For transmission, any complete or partial frame in the transmit cell FIFO is transmitted. For receive, frames that are detected by the EMAC after the suspend state is entered are ignored. No statistics are kept for ignored frames.

Table 8 shows how the SOFT and FREE bits affect the operation of the emulation suspend.

Table 8. Emulation Control

SOFT FREE Description

00 Normal operation

10 Emulation suspend

X 1 Normal operation

60 Ethernet Media Access Controller (EMAC)/Management Data Input/Output (MDIO) SPRUEQ6–December 2007

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