Texas Instruments VLYNQ Port - Manual (Page 24)

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2.14 Power Management
2.15 Emulation Considerations
Peripheral Architecture
The VLYNQ module can be placed in reduced-power modes to conserve power during periods of low
activity. The power management of the peripheral is controlled by the processor Power and Sleep
Controller (PSC). The PSC acts as a master controller for power management of all of the peripherals on
the processor.
The power conservation modes that are available via the PSC are:
•
Idle/Disabled state : Idle/disabled state stops the clocks from going to the peripheral and prevents all of
the register accesses. After re-enabling the peripheral from its idle state, all registers prior to setting in
the disabled state are restored and data transmission proceeds. Re-initialization is not required.
•
Synchronized reset : The synchronized reset state is similar to the power-on reset (POR) state. When
the processor is turned on, reset to the peripheral is asserted, then clocks to the peripheral are gated.
Registers reset to their default values. When powering-up after a synchronized reset, all of the VLYNQ
module registers must be reconfigured and the link must be re-established before data transmission.
For more detailed information on power management procedures using the PSC, see the
TMS320DM644x DMSoC ARM Subsystem Reference Guide (
SPRUE14 ).
If the serial clock is internally sourced, you can use the CLKDIV bit in the VLYNQ control register (CTRL)
to divide the serial clock down. This saves normal mode operation power consumption (at the expense of
reduced performance).
Additionally, the module provides the capability of auto-idling the serial clock domain (disable the VLYNQ
CLK) when the serial clock is sourced from the DM644x device and the VLYNQ SCRUN pin is connected
to the remote device. This allows power savings when there is no activity on the serial interface.
Note: There is no support for external wake-up for the VLYNQ module on the DM644x device. If
the VLYNQ module on the DM644x device has been disabled via the PSC, then even though
serial activity requests can be indicated from the remote VLYNQ device via the VLYNQ
SCRUN pin, it does not allow the serial clock (VLYNQ CLK) to be sourced until the VLYNQ
module is re-enabled via the PSC.
This can be configured by enabling the power management enable (PMEN) bit in the VLYNQ control
registers (CTRL, 0 = disable, 1 = enable) . This bit should only be set if the SCRUN pin is connected to
the remote VLYNQ device.
The SCRUN pin is a bi-directional pin which is driven low whenever there is serial activity on the local or
remote VLYNQ interface.
During debug, the ARM CPU may be halted for single stepping, bench marking, profiling, or other debug
uses using the emulator. VLYNQ does not support emulation halts/suspend operation. VLYNQ operations
continue during emulation halt/suspend.
VLYNQ Port 24 SPRUE36A – September 2007
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