TMS320F28027DAS datasheet(91/130 Pages) TI

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tw(RSL1)

th(boot-mode)(C)

(3.3V)

DDIO

DDA

INTOSC1

X1/X2

XRS

(D)

Boot-Mode

Pins

(1.8V)

XCLKOUT

I/OPins

User-codedependent

Boot-ROMexecutionstarts

Peripheral/GPIOfunction

Basedonbootcode

GPIOpinsasinput

GPIOpinsasinput(statedependsoninternalPU/PD)

OSCST

User-codedependent

Address/Data/

Control

(Internal)

Address/datavalid,internalboot-ROMcodeexecutionphase

User-codeexecutionphase

td(EX)

INTOSCST

(A)

(B)

TMS320F28027, TMS320F28026, TMS320F28023, TMS320F28022

TMS320F28021, TMS320F28020, TMS320F280200

www.ti.com

SPRS523F – NOVEMBER 2008 – REVISED DECEMBER 2010

6.9

Power Sequencing

There is no power sequencing requirement needed to ensure the device is in the proper state after reset

or to prevent the I/Os from glitching during power up/down. However, it is recommended that no voltage

larger than a diode drop (0.7 V) should be applied to any pin prior to powering up the device. Voltages

applied to pins on an unpowered device can bias internal p-n junctions in unintended ways and produce

unpredictable results.

Upon power up, SYSCLKOUT is OSCCLK/4. Since the XCLKOUTDIV bits in the XCLK register come up with a reset

state of 0, SYSCLKOUT is further divided by 4 before it appears at XCLKOUT. XCLKOUT = OSCCLK/16 during this

phase.

Boot ROM configures the DIVSEL bits for /1 operation. XCLKOUT = OSCCLK/4 during this phase. Note that

XCLKOUT will not be visible at the pin until explicitly configured by user code.

After reset, the boot ROM code samples Boot Mode pins. Based on the status of the Boot Mode pin, the boot code

branches to destination memory or boot code function. If boot ROM code executes after power-on conditions (in

debugger environment), the boot code execution time is based on the current SYSCLKOUT speed. The SYSCLKOUT

will be based on user environment and could be with or without PLL enabled.

Using the XRS pin is optional due to the on-chip power-on reset (POR) circuitry.

Figure 6-7. Power-on Reset

Electrical Specifications

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TMS320F28020 TMS320F280200

TMS320F28027DAS Datasheet(PDF) 91 Page - Texas Instruments

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