
–11–
REV. 0
ADSP-2191M
To exit Power-Down Core/Peripherals mode, the DSP responds 
to an interrupt and (after 500 cycles to restabilize the PLL) 
resumes executing instructions with the instruction after the 
IDLE.
Clock Signals
The ADSP-2191M can be clocked by a crystal oscillator or a 
buffered, shaped clock derived from an external clock oscillator. 
If a crystal oscillator is used, the crystal should be connected 
across the CLKIN and XTAL pins, with two capacitors and a 
1 M 
 shunt resistor connected as shown in 
Figure 3
. Capacitor 
values are dependent on crystal type and should be specified by 
the crystal manufacturer. A parallel-resonant, fundamental fre-
quency, microprocessor-grade crystal should be used for this 
configuration.
If a buffered, shaped clock is used, this external clock connects 
to the DSP’s CLKIN pin. CLKIN input cannot be halted, 
changed, or operated below the specified frequency during 
normal operation. When an external clock is used, the XTAL 
input must be left unconnected.
The DSP provides a user-programmable 1  to 32  multiplica-
tion of the input clock, including some fractional values, to 
support 128 external to internal (DSP core) clock ratios. The 
MSEL6–0, BYPASS, and DF pins decide the PLL multiplication 
factor at reset. At runtime, the multiplication factor can be con-
trolled in software. The combination of pullup and pull-down 
resistors in 
Figure
  sets up a core clock ratio of 6:1, which 
produces a 150 MHz core clock from the 25 MHz input. For 
other clock multiplier settings, see the 
ADSP-219x/2191 DSP 
Hardware Reference
.
The peripheral clock is supplied to the CLKOUT pin. 
All on-chip peripherals for the ADSP-2191M operate at the rate 
set by the peripheral clock. The peripheral clock is either equal 
to the core clock rate or one-half the DSP core clock rate. This 
selection is controlled by the IOSEL bit in the PLLCTL register. 
The maximum core clock is 160 MHz and the maximum periph-
eral clock is 80 MHz—the combination of the input clock and 
core/peripheral clock ratios may not exceed these limits.
Reset
The 
RESET
 signal initiates a master reset of the ADSP-2191M. 
The 
RESET
 signal must be asserted during the powerup 
sequence to assure proper initialization. 
RESET
 during initial 
powerup must be held long enough to allow the internal clock to 
stabilize. 
The powerup sequence is defined as the total time required for 
the crystal oscillator circuit to stabilize after a valid V
DD
 is applied 
to the processor, and for the internal phase-locked loop (PLL) to 
lock onto the specific crystal frequency. A minimum of 100 μs 
ensures that the PLL has locked, but does not include the crystal 
oscillator start-up time. During this powerup sequence the 
RESET
 signal should be held low. On any subsequent resets, the 
RESET
 signal must meet the minimum pulsewidth specifica- 
tion, t
WRST
. 
The 
RESET
 input contains some hysteresis. If using an RC 
circuit to generate your 
RESET
 signal, the circuit should use an 
external Schmidt trigger.
The master reset sets all internal stack pointers to the empty stack 
condition, masks all interrupts, and resets all registers to their 
default values (where applicable). When 
RESET
 is released, if 
there is no pending bus request and the chip is configured for 
booting, the boot-loading sequence is performed. Program 
control jumps to the location of the on-chip boot ROM 
(0xFF 0000).
Power Supplies
The ADSP-2191M has separate power supply connections for 
the internal (V
DDINT
) and external (V
DDEXT
) power supplies. 
The internal supply must meet the 2.5 V requirement. The 
external supply must be connected to a 3.3 V supply. All external 
supply pins must be connected to the same supply.
Powerup Sequence
Power up together the two supplies V
DDEXT
 and V
DDINT
. If 
they cannot be powered up together, power up the internal (core) 
supply first (powering up the core supply first reduces the risk of 
latchup events.
Booting Modes
The ADSP-2191M has five mechanisms (listed in 
Table 6
) for 
automatically loading internal program memory after reset. Two 
No-boot modes are also supported.
Figure 3. External Crystal Connections
CLKIN
CLKOUT
XTAL
ADSP-2191M
MSEL5 (PF5)
MSEL4 (PF4)
MSEL3 (PF3)
MSEL2 (PF2)
MSEL1 (PF1)
MSEL0 (PF0)
RESET
25MHz
MSEL6 (PF6)
DF (PF7)
V
DD
V
DD
BYPASS
RESET
SOURCE
RUNTIME
PF PIN I/O
THE PULL-UP/PULL-DOWN
RESISTORS ON THE MSEL,
DF, AND BYPASS PINS
SELECT THE CORE CLOCK
RATIO.
HERE, THE SELECTION (6:1)
AND 25MHz INPUT CLOCK
PRODUCE A 150MHz CORE
CLOCK.
1M