
Interrupt Control
Local Interrupt Control Unit
112
EPC User
’
s Manual Revision 1.05
Copyright 1997-2000, V3 Semiconductor Inc.
Figure 56
:
Local Interrupt Control Unit Block Diagram
13.1.2
Local Interrupt Requests
The following local interrupt requests are physically latched within the LB_ISTAT register:
"PCI_RD", "PCI_WR" bits: PCI Read and Write Error Interrupts
"DMA0", "DMA1" bits: DMA Channels 0 and 1 Interrupts
"MAILBOX" bit: Mailbox interrupt requests
1
The above interrupt requests are cleared by clearing (0) the corresponding bits in the
LB_ISTAT register.
The following local interrupts are not latched within the LB_ISTAT register:
"PCI_INT" bit: PCI interrupt control unit requests
Non-latched interrupt requests are only cleared when the source of the corresponding
interrupt request is cleared. For example, the PCI_INT request is only cleared when all
enabled PCI interrupt inputs are de-asserted.
13.1.3
Masking Local Interrupt Requests
Local interrupt requests can be masked (disabled) by clearing the corresponding bit in the
LB_IMASK register. The interrupt mask register controls (enables) which of the interrupt
requests posted in the request register actually generate an interrupt request.
13.1.4
Local Interrupt Event Signal
The LICU has a single output signal that is the logical OR of all unmasked interrupt requests.
1. The MAILBOX bit is not latched in silicon revision B2 or later.
Mailbox IRQ
(OR of all Mailbox IRQs)
PCI IRQ (from PICU)
(OR of all PCI INTx IRQs)
PCI Read IRQ
(PCI Read Failure)
PCI Write IRQ
(PCI Write Failure)
DMA Channel 1 IRQ
(DMA Channel 1 Chain Done)
DMA Channel 0 IRQ
(DMA Channel 0 Chain Done)
Local Interrupt
Status
Register
(LB_ISTAT)
Local Interrupt
Request Mask
Register
(LB_IMASK)
L
To LINT Pin
Local Interrupt
Event Signal