Datasheet

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
V
DD
PauV
DD
pins for internal logic.
V
DD_A
PauV
DD
pins for analog circuits. Pay critical attention to bypassing this supply.
V
DD_IO
PauV
DD
pins for I/O buffers.
V
REF
I au 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). V
REF
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 V
SS
. Tie
the decoupling capacitor between V
REF
input and V
SS
, as close to the DSP’s pins as possible. For
more information, see Filtering Reference Voltage and Clocks on Page 10.
V
SS
GauGround pins.
V
SS_A
G au Ground pins for analog circuits.
NC 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 V
SS
; epu = external pull-up approximately 10 k
to V
DD-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 BM
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.