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MPC8240 Integrated Processor User’s Manual
EPIC Serial Interrupt Interface
Note that initially, interrupt source 0 is sampled at the fifth S_CLK rising edge after S_RST
negates. Also, once S_RST is asserted, it is not asserted again until after an EPIC reset, and
the EPIC unit is subsequently programmed to serial mode again.
11.6.2 Serial Interrupt Timing Protocol
Figure 11.7 shows the relative timing for the serial interrupt interface signals.
Figure 11-3. Serial Interrupt Interface Protocol
11.6.3 Edge/Level Sensitivity of Serial Interrupts
The interrupt detection is individually programmable for each source to be edge- or
level-sensitive by writing the sense and polarity bits of the vector/priority register of the
particular interrupt source. Refer to Section 11.3.6.1, “Interrupt Pending Register
(IPR)—Non-programmable,” and the serial vector/priority register description in
Section 11.9.8.1, “Direct & Serial Interrupt Vector/Priority Registers (IVPRs, SVPRs),” for
more edge/level sensitivity information.
Note that for level-sensitive interrupts there is a potential race condition between an EOI
(end of interrupt) command for a specific interrupt source and the sampling of the same
specific interrupt source as inactive. Level-sensitive interrupts are cleared from an interrupt
priority register only when sampled as inactive; therefore, a second interrupt for the same
source may occur, although the specific interrupt has already been serviced.
Software can avoid this second interrupt by delaying the EOI command to the EPIC unit.
Depending on the interrupt source device being serviced, one possible software method is
to first clear the interrupt from the source before executing any other necessary read or write
transactions to service the interrupt device. In any case, the delay should be no less than 16
serial clocks after clearing the interrupt at the source device.
S_CLK
S_FRAME
S_INT
S_CLK
S_RST
S_INT
1
2
4
5
0
1
2
EPIC starts sampling
S_RST
S_FRAME
3
4
5
7
8
9
10 11 12 13
3
6
14 15
serial interrupts here.
0
1
MPC8240
EPIC Unit
External Logic
Serial Interrupt
source 0
source 15
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 ...