Texas Instruments OMAP36 Series, Техническое справочное руководство

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PRCM Use Cases and Tips
NOTE: sys_nvmode1 and sys_nvmode2 are managed as one signal from the PRCM standpoint. In
other words, their settings and assertion conditions are managed globally, without any
granularity. The power IC software sets different values for VDD1 and VDD2, if necessary.
From the PRCM standpoint, using the VMODE signals is mutually exclusive with using the dedicated I2C4
interface to the external power IC; sys_nvmodex signals share the same physical interface as I2C4 at
device boundary.
Using VMODE voltage control is an easy way to switch VDD1 and VDD2 voltage values upon device
power state transitions. The following section gives the programming steps to achieve voltage
management through VMODE signals.
3.7.2.2 Programming Sequence
3.7.2.2.1 Initialization Procedure
1. Configure sys_nvmode1 and sys_nvmode2 at the device level.
CONTROL.CONTROL_PADCONF_I2C4_SCL[15:0] Mux mode1
CONTROL.CONTROL_PADCONF_I2C4_SCL[31:16] Mux mode1
The correct multiplexing mode is selected at the device level to select sys_nvmode1 and sys_nvmode2
on the balls. This is done in the SCM registers, as indicated. For further details, see
Chapter 13 ,
System Control Module.
2. Activate VMODE control.
PRM_VOLTCTRL [4] SEL_VMODE 0x1
VMODE control is selected in the PRCM module. This also ensures the other interfaces to the power
IC are correctly deactivated and managed.
3. Set the polarity of sys_nvmode1 and sys_nvmode2.
PRM_POLCTRL [0] EXTVOL_POL 0x1 => sys_nvmodex signals are active high
Depending on the polarity set, the VMODE signals remain high or low until a transition is initiated.
Their states then automatically toggle to the opposite state and return when the reverse transition is
initiated.
4. Set the voltage stabilization delays.
PRM_VOLTSETUP1 [31:16] SETUP_TIME2 VDD2 voltage stabilization time
PRM_VOLTSETUP1 [15:0] SETUP_TIME1 VDD1 voltage stabilization time
SETUP_TIME1 and SETUP_TIME2 are power IC-dependent parameters for voltage stabilization time
for VDD1 and VDD2, respectively. For further details, see the power IC documentation.
5. Configure the power IC.
This step relies entirely on power IC software settings. The purpose here is to link a voltage value to
both VDD1 and VDD2 depending on the state of the sys_nvmodex signals. For further details, see the
power IC documentation.
3.7.2.2.2 VMODE Signals Toggling
1. Has a sleep/wake-up transition been initiated?
As stated previously, when VMODE voltage control is selected, the PRCM module automatically
toggles sys_nvmodex signals and device sleep and wake-up transitions. This means the user has
nothing more to control except the device transitions, as explained in this document. When a transition
is initiated, sys_nvmode1 and sys_nvmode2 toggle according to their programmed polarity and alert
the power IC to switch VDD1 and VDD2 to the programmed values.
2. Wait for stabilization time.
Depending on the SETUP_TIME1 and SETUP_TIME2 settings, the PRCM module starts a countdown
immediately after the VMODE signal state changes. This ensures that the voltages provided by the
power IC are stable before switching the device to the desired power state.
457 SWPU177N – December 2009 – Revised November 2010 Power, Reset, and Clock Management
Copyright © 2009–2010, Texas Instruments Incorporated