adsp-21992 Analog Devices, Inc., adsp-21992 Datasheet - Page 14

• Manufacturer Part Number: adsp-21992
• Description: Mixed Signal Dsp Controller With Can
• Manufacturer: Analog Devices, Inc.

ADSP-21992
from an external source using the RESET signal, or alterna-
tively, the internal power-on reset circuit may be used by
connecting the POR pin to the RESET pin. During power-up
the RESET line must be activated for long enough to allow the
DSP core’s internal clock to stabilize. The power-up sequence is
defined as the total time required for the crystal oscillator to sta-
bilize after a valid VDD is applied to the processor and for the
internal phase-locked loop (PLL) to lock onto the specific crys-
tal frequency. A minimum of 512 cycles will ensure that the PLL
has locked (this does not include the crystal oscillator
start-up time).
The RESET input contains some hysteresis. If an RC circuit is
used to generate the RESET signal, the circuit should use an
external Schmitt 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, program control
jumps to the location of the on-chip boot ROM (0xFF0000) and
the booting sequence is performed.
POWER SUPPLIES
The ADSP-21992 has separate power supply connections for the
internal (V
internal supply must meet the 2.5 V requirement. The external
supply must be connected to a 3.3 V supply. All external supply
Table 3. Summary of Boot Modes
Boot Mode
0
1
2
3
4
5
6
7
DDINT
) and external (V
BMODE2
0
0
0
0
1
1
1
1
BMODE1
0
0
1
1
0
0
1
1
DDEXT
) power supplies. The
BMODE0
0
1
0
1
0
1
0
1
Rev. A | Page 14 of 60 | August 2007
Function
Illegal–Reserved
Boot from External 8-Bit Memory over EMI
Execute from External 8-Bit Memory
Execute from External 16-Bit Memory
Boot from SPI
Boot from SPI
Illegal–Reserved
Illegal–Reserved
pins must be connected to the same supply. The ideal power-on
sequence for the DSP is to provide power-up of all supplies
simultaneously. If there is going to be some delay in power-up
between the supplies, provide V
BOOTING MODES
The ADSP-21992 supports a number of different boot modes
that are controlled by the three dedicated hardware boot mode
control pins (BMODE2, BMODE1, and BMODE0). The use of
three boot mode control pins means that up to eight different
boot modes are possible. Of these only five modes are valid on
the ADSP-21992. The ADSP-21992 exposes the boot mecha-
nism to software control by providing a nonmaskable boot
interrupt that vectors to the start of the on-chip ROM memory
block (at address 0xFF0000). A boot interrupt is automatically
initiated following either a hardware initiated reset, via the
RESET pin, or a software initiated reset, via writing to the soft-
ware reset register. Following either a hardware or a software
reset, execution always starts from the boot ROM at address
0xFF0000, irrespective of the settings of the BMODE2,
BMODE1, and BMODE0 pins. The dedicated BMODE2,
BMODE1, and BMODE0 pins are sampled at hardware reset.
The particular boot mode for the ADSP-21992 associated with
the settings of the BMODE2, BMODE1, BMODE0 pins is
defined in
≤
>
4K Bits
4K Bits
Table
3.
DD
first, then V
DD_IO
.