dsp56800eerm Freescale Semiconductor, Inc, dsp56800eerm Datasheet - Page 77

• Manufacturer Part Number: dsp56800eerm
• Description: 16-bit Digital Signal Controllers
• Manufacturer: Freescale Semiconductor, Inc

5.3.2
Interrupt exceptions may be nested to allow an IRQ of higher priority than the current exception to be
serviced. The following tables define the nesting requirements for each priority level.
5.3.3
Fast interrupts are described in the DSP56800E Reference Manual. The interrupt controller recognizes
fast interrupts before the core does.
A fast interrupt is defined (to the ITCN) by:
When an interrupt occurs, its vector number is compared with the FIM0 and FIM1 register values. If a
match occurs, and it is a level 2 interrupt, the ITCN handles it as a fast interrupt. The ITCN takes the vector
address from the appropriate FIVALn and FIVAHn registers, instead of generating an address that is an
offset from the VBA.
The core then fetches the instruction from the indicated vector adddress and if it is not a JSR, the core starts
its fast interrupt handling.
Freescale Semiconductor
Preliminary
1. Setting the priority of the interrupt as level 2, with the appropriate field in the IPR registers
2. Setting the FIMn register to the appropriate vector number
3. Setting the FIVALn and FIVAHn registers with the address of the code for the fast interrupt
1. Core status register bits indicating current interrupt mask within the core.
Interrupt Nesting
Fast Interrupt Handling
SR[9]
1. See IPIC field definition in
0
0
1
1
IPIC_LEVEL[1:0]
1
00
01
01
11
Table 5-2. Interrupt Priority Encoding
Table 5-1 Interrupt Mask Bit Definition
SR[8]
0
1
0
1
1
1
No Interrupt or SWILP
Priority 0
Priority 1
Priorities 2 or 3
56F8357 Technical Data, Rev. 15
Current Interrupt Priority
Part 5.6.30.2
Priorities 0, 1, 2, 3
Priorities 1, 2, 3
Priorities 2, 3
Priority 3
Permitted Exceptions
Level
Priorities 0, 1, 2, 3
Priorities 1, 2, 3
Priorities 2, 3
Priority 3
Exception Priority
Required Nested
None
Priority 0
Priorities 0, 1
Priorities 0, 1, 2
Masked Exceptions
Functional Description
77