
ADSP-2191M
–10–
REV. 0
Programmable Flag (PFx) Pins
The ADSP-2191M has 16 bidirectional, general-purpose I/O, 
Programmable Flag (PF15–0) pins. The PF7–0 pins are 
dedicated to general-purpose I/O. The PF15–8 pins serve either 
as general-purpose I/O pins (if the DSP is connected to an 8-bit 
external data bus) or serve as DATA15–8 lines (if the DSP is 
connected to a 16-bit external data bus). The Programmable Flag 
pins have special functions for clock multiplier selection and for 
SPI port operation. For more information, see 
Serial Peripheral 
Interface (SPI) Ports on page 9
 and 
Clock Signals on page 11
. 
Ten memory-mapped registers control operation of the Program-
mable Flag pins:
 Flag Direction register
Specifies the direction of each individual PFx pin as input 
or output. 
 Flag Control and Status registers
Specify the value to drive on each individual PFx output 
pin. As input, software can predicate instruction 
execution on the value of individual PFx input pins 
captured in this register. One register sets bits, and one 
register clears bits.
 Flag Interrupt Mask registers
Enable and disable each individual PFx pin to function 
as an interrupt to the DSP’s core. One register sets bits to 
enable interrupt function, and one register clears bits to 
disable interrupt function. Input PFx pins function as 
hardware interrupts, and output PFx pins function as 
software interrupts—latching in the IMASK and IRPTL 
registers.
 Flag Interrupt Polarity register
Specifies the polarity (active high or low) for interrupt 
sensitivity on each individual PFx pin. 
 Flag Sensitivity registers
Specify whether individual PFx pins are level- or 
edge-sensitive and specify—if edge-sensitive—whether 
just the rising edge or both the rising and falling edges of 
the signal are significant. One register selects the type of 
sensitivity, and one register selects which edges are signif-
icant for edge-sensitivity.
Low Power Operation
The ADSP-2191M has four low-power options that significantly 
reduce the power dissipation when the device operates under 
standby conditions. To enter any of these modes, the DSP 
executes an IDLE instruction. The ADSP-2191M uses configu-
ration of the PDWN, STOPCK, and STOPALL bits in the 
PLLCTL register to select between the low-power modes as the 
DSP executes the IDLE. Depending on the mode, an IDLE shuts 
off clocks to different parts of the DSP in the different modes. 
The low power modes are:
 Idle
 Power-Down Core
 Power-Down Core/Peripherals
 Power-Down All
Idle Mode
When the ADSP-2191M is in Idle mode, the DSP core stops 
executing instructions, retains the contents of the instruction 
pipeline, and waits for an interrupt. The core clock and peripheral 
clock continue running. 
To enter Idle mode, the DSP can execute the IDLE instruction 
anywhere in code. To exit Idle mode, the DSP responds to an 
interrupt and (after two cycles of latency) resumes executing 
instructions with the instruction after the IDLE.
Power-Down Core Mode
When the ADSP-2191M is in Power-Down Core mode, the DSP 
core clock is off, but the DSP retains the contents of the pipeline 
and keeps the PLL running. The peripheral bus keeps running, 
letting the peripherals receive data. 
To enter Power-Down Core mode, the DSP executes an IDLE 
instruction after performing the following tasks:
 Enter a power-down interrupt service routine
 Check for pending interrupts and I/O service routines
 Clear (= 0) the PDWN bit in the PLLCTL register
 Clear (= 0) the STOPALL bit in the PLLCTL register
 Set (= 1) the STOPCK bit in the PLLCTL register
To exit Power-Down Core mode, the DSP responds to an 
interrupt and (after two cycles of latency) resumes executing 
instructions with the instruction after the IDLE.
Power-Down Core/Peripherals Mode
When the ADSP-2191M is in Power-Down Core/Peripherals 
mode, the DSP core clock and peripheral bus clock are off, but 
the DSP keeps the PLL running. The DSP does not retain the 
contents of the instruction pipeline.The peripheral bus is 
stopped, so the peripherals cannot receive data.
To enter Power-Down Core/Peripherals mode, the DSP executes 
an IDLE instruction after performing the following tasks:
 Enter a power-down interrupt service routine
 Check for pending interrupts and I/O service routines
 Clear (= 0) the PDWN bit in the PLLCTL register
 Set (= 1) the STOPALL bit in the PLLCTL register
To exit Power-Down Core/Peripherals mode, the DSP responds 
to a wake-up event and (after five to six cycles of latency) resumes 
executing instructions with the instruction after the IDLE.
Power-Down All Mode
When the ADSP-2191M is in Power-Down All mode, the DSP 
core clock, the peripheral clock, and the PLL are all stopped. The 
DSP does not retain the contents of the instruction pipeline. The 
peripheral bus is stopped, so the peripherals cannot receive data.
To enter Power-Down All mode, the DSP executes an IDLE 
instruction after performing the following tasks:
 Enter a power-down interrupt service routine
 Check for pending interrupts and I/O service routines
 Set (= 1) the PDWN bit in the PLLCTL register