Chapter 11. Embedded Programmable Interrupt Controller (EPIC) Unit
11-7
EPIC Unit Interrupt Protocol
11.3 EPIC Unit Interrupt Protocol
The following sections describe the priority of interrupts controlled by the EPIC unit, the
interrupt acknowledge mechanism, the nesting of multiple interrupts, and the handling of
spurious interrupts.
11.3.1 Interrupt Source Priority
The software assigns a priority value to each interrupt source by writing to the
vector/priority register for the particular source. Priority values are in the range 0 to 15 of
which 15 is the highest. In order for an interrupt to be signalled to the processor, the priority
of the source must be greater than that of the current task priority of the processor (and the
in-service interrupt source priority). Therefore, setting a source priority to zero inhibits that
interrupt.
The EPIC unit services simultaneous interrupts occurring with the same priority according
to the following set order: timer 0–timer 3, DMA 0, DMA 1, MU, I
2
C, direct interrupts
from IRQ[0:4] (or serial interrupt source).
11.3.2 Processor Current Task Priority
The EPIC unit has a processor current task priority register (PCTPR) set by system software
to indicate the relative importance of the task running on the processor. When an interrupt
has a priority level greater than the current task priority (and the in-service interrupt source
priority), it is signalled to the processor. Therefore, setting the task priority to 15 in the
PCTPR prevents the signalling of any interrupt to the processor.
0x5_10D0
Message unit interrupt destination register (IIDR3)
P0
0x5_10E0–0x5_FFF0
Reserved
—
Table 11-4. EPIC Register Address Map—Processor-Related Registers
Address Offset
from EUMBBAR
Register Name
Field Mnemonics
0x6_0000–0x6_0070
Reserved
—
0x6_0080
Processor current task priority register (PCTPR)
TASKP
0x6_0090
Reserved
—
0x6_00A0
Processor interrupt acknowledge register (IACK)
VECTOR
0x6_00B0
Processor end-of-interrupt register (EOI)
EOI_CODE
0x6_00C0–0x6_3FF0
Reserved
—
Table 11-3. EPIC Register Address Map—Interrupt Source
Configuration Registers (Continued)
Address Offset
from EUMBBAR
Register Name
Field Mnemonics
Summary of Contents for MPC8240
Page 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Page 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Page 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Page 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Page 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Page 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Page 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Page 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Page 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Page 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Page 516: ...16 14 Watchpoint Trigger Applications ...
Page 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Page 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Page 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...