TMS320C6421_07 Datasheet, PDF (143/227 Pages) Texas Instruments – Fixed-Point Digital Signal Processor

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TMS320C6421
Fixed-Point Digital Signal Processor
SPRS346B – JANUARY 2007 – REVISED APRIL 2007
6.5.8 Pin Behaviors at Reset
During normal operations, pins are controlled by the respective peripheral selected in the PINMUX0 or
PINMUX1 register. During device level global reset, the pin behaves as follows:
Multiplexed Boot and Configuration Pins
These pins are forced 3-stated when RESETOUT is asserted (low). This is to ensure the proper boot and
configuration values can be latched on these multiplexed pins. This is particularly useful in the case where
the boot and configuration values are driven by an external control device. After RESETOUT is
deasserted (high), these pins are controlled by their respective default peripheral.
• Boot and Configuration Pins Group: RMTXD0/GP[28], RMTXD1/GP[27](LENDIAN),
GP[26]/(FASTBOOT), GP[25]/(BOOTMODE3), GP[24]/(BOOTMODE2), GP[23]/(BOOTMODE1),
GP[22]/(BOOTMODE0), EM_A[4]/GP[10]/(PLLMS2), EM_A[1]/(ALE)/GP[9]/(PLLMS1),
EM_A[2]/(CLE)/GP[8]/(PLLMS0), EM_A[0]/GP[7]/(AEM2), EM_BA[0]/GP[6]/(AEM1), and
EM_BA[1]/GP[5]/(AEM0).
For information on whether external pullup/pulldown resistors should be used on the boot and
configuration pins, see Section 3.9.1, Pullup/Pulldown Resistors.
Default Power Down Pins
As discussed in Section 3.2, Power Considerations, the VDD3P3V_PWDN register controls power to the
3.3-V pins. The VDD3P3V_PWDN register defaults to powering down some 3.3-V pins to save power. For
more details on the VDD3P3V_PWDN register and which 3.3-V pins default to powerup or powerdown,
Section 3.2, Power Considerations. The pins that default to powerdown, are both reset to powerdown and
high-impedance. They remain in that state until configured otherwise by VDD3P3_PWDN and
PINMUX0/PINMUX1 programming.
• Default Power Down Pin Group: GP[4]/PWM1, ACLKR0/CLKX0/GP[99], AFSR0/DR0/GP[100],
AHCLKR0/CLKR0/GP[101], AXR0[3]/FSR0/GP[102], AXR0[2]/FSX0/GP[103], AXR0[1]/DX0/GP[104],
AXR0/ GP[105], ACLKX0/GP[106], AFSX0/GP[107], AHCLKX0/GP[108], AMUTEIN0/GP[109],
AMUTE0/GP[110], TOUT1L/GP[55], TINP1L/GP[56], CLKS0/TOUT0L/GP[97], TINP0L/GP[98],
URXD0/GP[85], UTXD0/GP[86], UCTS0/GP[87], and URTS0/PWM0/GP[88].
All Other Pins
During RESETOUT assertion (low), all other pins are controlled by the default peripheral. The default
peripheral is determined by the default settings of the PINMUX0 or PINMUX1 registers.
Some of the PINMUX0/PINMUX1 settings are determined by configuration pins latched at reset. To
determine the reset behavior of these pins, see Section 3.7, Multiplexed Pin Configurations and read the
rest of the this subsection to understand how that default peripheral controls the pin.
The reset behaviors for all these other pins are categorized as follows (also see Figure 6-7 and Figure 6-8
in Section 6.5.9, Reset Electrical Data/Timing):
• Z+/Low Group (Z Longer-to-Low Group): These pins are 3-stated when device-level global reset
source (e.g., POR, RESET or Max Reset) is asserted. These pins remain 3-stated throughout
RESETOUT assertion. When RESETOUT is deasserted, these pins drive a logic low.
• Z+/High Group (Z Longer-to-High Group): These pins are 3-stated when device-level global reset
source (e.g., POR, RESETor Max Reset) is asserted. These pins remain 3-stated throughout
RESETOUT assertion. When RESETOUT is deasserted, these pins drive a logic high.
• Z+/Invalid Group (Z Longer-to-Invalid Group): These pins are 3-stated when device-level global
reset source (e.g., POR, RESETor Max Reset) is asserted. These pins remain 3-stated throughout
RESETOUT assertion. When RESETOUT is deasserted, these pins drive an invalid value until
configured otherwise by their respective peripheral (after the peripheral is enabled by the PSC).
• Z Group: These pins are 3-stated by default, and these pins remain 3-stated throughout RESETOUT
assertion. When RESETOUT is deasserted, these pins remain 3-stated until configured otherwise by
their respective peripheral (after the peripheral is enabled by the PSC).
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Peripheral Information and Electrical Specifications 143