Analog Devices TigerSHARC ADSP-TS201S - Manual (Page 20)

Rev. C | Page 20 of 48 | December 2006
ADSP-TS201S
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 internal pull-up or pull-down
for the default value. If a strap pin is not connected to an over-
driving external pull-up, pull-down, or logic load, the DSP
samples the default value during reset. If strap pins are connected to logic inputs, a stronger external pull-up or 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 or pull-down.
Table 16
lists and describes each of the DSP’s strap pins.
When default configuration is used, no external resistor is
needed on the strap pins. To apply other configurations, a
500
Ω resistor connected to V
DD_IO
is required. If providing
external pull-downs, do not strap these pins directly to V
SS
; the
strap pins require 500 Ω resistor straps.
All strap pins are sampled on the rising edge of RST_IN (deas-
sertion edge). Each pin latches the strapped pin state (state of
the strap pin at the rising edge of RST_IN). Shortly after deas-
sertion of RST_IN, these pins are reconfigured to their normal
functionality.
These strap pins have an internal pull-down resistor, pull-up
resistor, or no-resistor (three-state) on each pin. The resistor
type, which is connected to the I/O pad, depends on whether
RST_IN is active (low) or if RST_IN is deasserted (high).
Table 17 shows the resistors that are enabled during active reset
and during normal operation.
Table 16. Pin Definitions—I/O Strap Pins
Signal
Type (at
Reset)
On Pin … Description
EBOOT I
(pd_0) 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 I
(pd) BM Interrupt Enable.
0 = disable and set IRQ3–0 interrupts to edge-sensitive after
reset (default)
1 = enable and set IRQ3–0 interrupts to level-sensitive
immediately after reset
LINK_DWIDTH I
(pd) TMR0E Link Port Input Default Data Width.
0 = 1-bit (default)
1 = 4-bit
SYS_REG_WE I
(pd_0) BUSLOCK SYSCON and SDRCON Write Enable.
0 = one-time writable after reset (default)
1 = always writable
TM1 I
(pu) L1BCMPO Test Mode 1. Do not overdrive default value during reset.
TM2 I
(pu) L2BCMPO Test Mode 2. Do not overdrive default value during reset.
TM3 I
(pu) L3BCMPO Test Mode 3. Do not overdrive default value during reset.
I = input; A = asynchronous; O = output; OD = open-drain output; T = three-state; P = power supply; G = ground; pd = internal pull-down
5 k
Ω ; pu = internal pull-up 5 k Ω ; pd_0 = internal pull-down 5 k Ω on DSP ID = 0; pu_0 = internal pull-up 5 k Ω on DSP ID = 0; pu_od_0 = internal
pull-up 500 Ω on DSP ID = 0; pd_m = internal pull-down 5 k Ω on DSP bus master; pu_m = internal pull-up 5 k Ω on DSP bus master; pu_ad
= internal pull-up 40 k Ω . For more pull-down and pull-up information, see Electrical Characteristics on Page 22 .
Table 17. Strap Pin Internal Resistors—Active Reset
(RST_IN = 0) vs. Normal Operation (RST_IN = 1)
Pin RST_IN = 0 RST_IN = 1
BMS (pd_0) (pu_0)
BM (pd) Driven
TMR0E (pd) Driven
BUSLOCK (pd_0) (pu_0)
L1BCMPO (pu) Driven
L2BCMPO (pu) Driven
L3BCMPO (pu) Driven
pd = internal pull-down 5 k Ω ; pu = internal pull-up 5 k Ω ;
pd_0 = internal pull-down 5 k Ω on DSP ID = 0;
pu_0 = internal pull-up 5 k Ω on DSP ID = 0