
SPRS094I  APRIL 1999  REVISED SEPTEMBER 2003
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device reset and interrupts
The TMS320x240x software-programmable interrupt structure supports flexible on-chip and external interrupt
configurations to meet real-time interrupt-driven application requirements. The LF240x recognizes three types of
interrupt sources.
Reset 
(hardware- or software-initiated) is unarbitrated by the CPU and takes immediate priority over any
other executing functions. All maskable interrupts are disabled until the reset service routine enables them.
The LF240x devices have two sources of reset: an external reset pin and a watchdog timer time-out (reset).
Hardware-generated interrupts
 are requested by external pins or by on-chip peripherals. There are two
types:
External interrupts
 are generated by one of four external pins corresponding to the interrupts XINT1,
XINT2, PDPINTA, and PDPINTB. These four can be masked both by dedicated enable bits and by the
CPU’s interrupt mask register (IMR), which can mask each maskable interrupt line at the DSP core.
Peripheral interrupts
are initiated internally by these on-chip peripheral modules: event manager A,
event manager B, SPI, SCI, CAN, and ADC. They can be masked both by enable bits for each event in
each peripheral and by the CPU’s IMR, which can mask each maskable interrupt line at the DSP core.
Software-generated interrupts
 for the LF240x devices include:
The INTR instruction.
 This instruction allows initialization of any LF240x interrupt with software. Its
operand indicates the interrupt vector location to which the CPU branches. This instruction globally
disables maskable interrupts (sets the INTM bit to 1).
The NMI instruction.
 This instruction forces a branch to interrupt vector location 24h. This instruction
globally disables maskable interrupts. 240x devices do not have the NMI hardware signal, only software
activation is provided.
The TRAP instruction.
 This instruction forces the CPU to branch to interrupt vector location 22h. The
TRAP instruction does 
not
 disable maskable interrupts (INTM is not set to 1); therefore, when the CPU
branches to the interrupt service routine, that routine can be interrupted by the maskable hardware
interrupts.
An emulator trap. 
This interrupt can be generated with either an INTR instruction or a TRAP instruction.
Six core interrupts (INT1INT6) are expanded using a peripheral interrupt expansion (PIE) module identical to
the F24x devices. The PIE manages all the peripheral interrupts from the 240x peripherals and are grouped to
share the six core level interrupts. Figure 4 shows the PIE block diagram for hardware-generated interrupts.
The PIE block diagram (Figure 4) and the interrupt table (Table 3) explain the grouping and interrupt vector
maps. LF240x devices have  interrupts identical to those of the F24x devices and should be completely
code-compatible. 240x devices also have peripheral interrupts identical to those of the F24x  plus additional
interrupts for new peripherals such as event manager B. Though the new interrupts share the 24x interrupt
grouping, they all have a unique vector to differentiate among the interrupts. See Table 3 for details.