
DSP56321 Technical Data, Rev. 11
1-6
Freescale Semiconductor
Signals/Connections
1.5  Interrupt and Mode Control
The interrupt and mode control signals select the chip operating mode as it comes out of hardware reset. After 
RESET is deasserted, these inputs are hardware interrupt request lines.
Table 1-8.     
Interrupt and Mode Control
Signal Name
Type
State During 
Reset
Signal Description
MODA
IRQA
Input
Input
Schmitt-trigger 
Input
Mode Select A
—MODA, MODB, MODC, and MODD select one of 16 initial 
chip operating modes, latched into the Operating Mode Register when the 
RESET signal is deasserted.
External Interrupt Request A
—After reset, this input becomes a level-
sensitive or negative-edge-triggered, maskable interrupt request input during 
normal instruction processing. If the processor is in the STOP or WAIT 
standby state and IRQA is asserted, the processor exits the STOP or WAIT 
state. 
MODB
IRQB
Input
Input
Schmitt-trigger 
Input
Mode Select B
—MODA, MODB, MODC, and MODD select one of 16 initial 
chip operating modes, latched into the Operating Mode Register when the 
RESET signal is deasserted.
External Interrupt Request B
—After reset, this input becomes a level-
sensitive or negative-edge-triggered, maskable interrupt request input during 
normal instruction processing. If the processor is in the WAIT standby state 
and IRQB is asserted, the processor exits the WAIT state. 
MODC
IRQC
Input
Input
Schmitt-trigger 
Input
Mode Select C
—MODA, MODB, MODC, and MODD select one of 16 initial 
chip operating modes, latched into the Operating Mode Register when the 
RESET signal is deasserted.
External Interrupt Request C
—After reset, this input becomes a level-
sensitive or negative-edge-triggered, maskable interrupt request input during 
normal instruction processing. If the processor is in the WAIT standby state 
and IRQC is asserted, the processor exits the WAIT state. 
MODD
IRQD
Input
Input
Schmitt-trigger 
Input
Mode Select D
—MODA, MODB, MODC, and MODD select one of 16 initial 
chip operating modes, latched into the Operating Mode Register when the 
RESET signal is deasserted.
External Interrupt Request D
—After reset, this input becomes a level-
sensitive or negative-edge-triggered, maskable interrupt request input during 
normal instruction processing. If the processor is in the WAIT standby state 
and IRQD is asserted, the processor exits the WAIT state. 
RESET
Input
Schmitt-trigger 
Input
Reset
—Places the chip in the Reset state and resets the internal phase 
generator. The Schmitt-trigger input allows a slowly rising input (such as a 
capacitor charging) to reset the chip reliably. When the RESET signal is 
deasserted, the initial chip operating mode is latched from the MODA, MODB, 
MODC, and MODD inputs. The RESET signal must be asserted after 
powerup.
PINIT
NMI
Input
Input
Schmitt-trigger 
Input
PLL Initial
—During assertion of RESET, the value of PINIT determines 
whether the DPLL is enabled or disabled. 
Nonmaskable Interrupt
—After RESET deassertion and during normal 
instruction processing, this Schmitt-trigger input is the negative-edge-triggered 
NMI request.