ADSP-TS101S datasheet(19/48 Pages) AD

19 / 48 page

ADSP-TS101S

Rev. C

Page 19 of 48

May 2009

STRAP PIN FUNCTION DESCRIPTIONS

Some pins have alternate functions at reset. Strap options set

DSP operating modes. During reset, the DSP samples the strap

option pins. Strap pins have an approximately 100 k pull-

down for the default value. If a strap pin is not connected to an

external pull-up or logic load, the DSP samples the default value

during reset. If strap pins are connected to logic inputs, a stron-

ger external pull-down may be required to ensure default value

depending on leakage and/or low level input current of the logic

load. To set a mode other than the default mode, connect the

strap pin to a sufficiently stronger external pull-up. In a multi-

processor system, up to eight DSPs may be connected on the

cluster bus, resulting in parallel combination of strap pin pull-

down resistors. Table 16 lists and describes each of the DSP’s

strap pins.

Table 15. Pin Definitions—Power, Ground, and Reference

Signal

Type

Term

Description

VDD

Pau

VDD pins for internal logic.

VDD_A

Pau

VDD pins for analog circuits. Pay critical attention to bypassing this supply.

VDD_IO

Pau

VDD pins for I/O buffers.

VREF

Reference voltage defines the trip point for all input buffers, except RESET, IRQ3–0, DMAR3–0,

ID2–0, CONTROLIMP2–0, TCK, TDI, TMS, and TRST. The value is 1.5 V ± 100 mV (which is the TTL

trip point). VREF can be connected to a power supply or set by a voltage divider circuit. The

voltage divider should have an HF decoupling capacitor (1 nF HF SMD) connected to VSS. Tie

the decoupling capacitor between VREF input and VSS, as close to the DSP’s pins as possible. For

more information, see Filtering Reference Voltage and Clocks on Page 10.

VSS

Gau

Ground pins.

VSS_A

Ground pins for analog circuits.

No connect. Do not connect these pins to anything (not to any supply, signal, or each other),

because they are reserved and must be left unconnected.

Type column symbols: A = asynchronous; G = ground; I = input; O = output; o/d = open drain output; P = power supply;

pd = internal pull-down approximately 100 k; pu = internal pull-up approximately 100 k; T = three-state

Term (for termination) column symbols: epd = external pull-down approximately 10 k to VSS; epu = external pull-up approximately 10 k

to VDD-IO, nc = not connected; au = always used.

Table 16. Pin Definitions—I/O Strap Pins

Signal

On Pin …

Description

EBOOT

BMS

EPROM boot.

0 = boot from EPROM immediately after reset (default)

1 = idle after reset and wait for an external device to boot DSP through the

external port or a link port

IRQEN

Interrupt Enable.

0 = disable and set IRQ3–0 interrupts to level sensitive after reset (default)

1 = enable and set IRQ3–0 interrupts to edge sensitive immediately after reset

TM1

L2DIR

Test Mode 1.

0 = required setting during reset.

1 = reserved.

TM2

TMR0E

Test Mode 2.

0 = required setting during reset.

1 = reserved.

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