High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
Chapter 5 System Interrupts
5.1
Functional Overview
This chapter describes the system interrupt structure of the LAN9312. The LAN9312 provides a multi-
tier programmable interrupt structure which is controlled by the System Interrupt Controller. The
programmable system interrupts are generated internally by the various LAN9312 sub-modules and
can be configured to generate a single external host interrupt via the IRQ interrupt output pin. The
programmable nature of the host interrupt provides the user with the ability to optimize performance
dependent upon the application requirements. The IRQ interrupt buffer type, polarity, and de-assertion
interval are modifiable. The IRQ interrupt can be configured as an open-drain output to facilitate the
sharing of interrupts with other devices. All internal interrupts are maskable and capable of triggering
the IRQ interrupt.
5.2
Interrupt Sources
The LAN9312 is capable of generating the following interrupt types:
1588 Time Stamp Interrupts (Port 2,1,0 and GPIO 9,8)
Switch Fabric Interrupts (Buffer Manager, Switch Engine, and Port 2,1,0 MACs)
Ethernet PHY Interrupts (Port 1,2 PHYs)
GPIO Interrupts (GPIO[11:0])
Host MAC Interrupts (FIFOs)
Power Management Interrupts
General Purpose Timer Interrupt (GPT)
Software Interrupt (General Purpose)
Device Ready Interrupt
All interrupts are accessed and configured via registers arranged into a multi-tier, branch-like structure,
as shown in Figure 5.1. At the top level of the LAN9312 interrupt structure are the Interrupt Status
Register (INT_STS), Interrupt Enable Register (INT_EN), and Interrupt Configuration Register
(IRQ_CFG).
The Interrupt Status Register (INT_STS) and Interrupt Enable Register (INT_EN) aggregate and
enable/disable all interrupts from the various LAN9312 sub-modules, combining them together to
create the IRQ interrupt. These registers provide direct interrupt access/configuration to the Host MAC,
General Purpose Timer, software, and device ready interrupts. These interrupts can be monitored,
enabled/disabled, and cleared, directly within these two registers. In addition, interrupt event
indications are provided for the 1588 Time Stamp, Switch Fabric, Port 1 & 2 Ethernet PHYs, Power
Management, and GPIO interrupts. These interrupts differ in that the interrupt sources are generated
and cleared in other sub-block registers. The INT_STS register does not provide details on what
specific event within the sub-module caused the interrupt, and requires the software to poll an
additional sub-module interrupt register (as shown in Figure 5.1) to determine the exact interrupt
source and clear it. For interrupts which involve multiple registers, only after the interrupt has been
serviced and cleared at its source will it be cleared in the INT_STS register.
The Interrupt Configuration Register (IRQ_CFG) is responsible for enabling/disabling the IRQ interrupt
output pin as well as configuring its properties. The IRQ_CFG register allows the modification of the
IRQ pin buffer type, polarity, and de-assertion interval. The de-assertion timer guarantees a minimum
interrupt de-assertion period for the IRQ output and is programmable via the INT_DEAS field of the
Interrupt Configuration Register (IRQ_CFG). A setting of all zeros disables the de-assertion timer. The
de-assertion interval starts when the IRQ pin de-asserts, regardless of the reason.
Note: The de-assertion timer does not apply to the PME interrupt. Assertion of the PME interrupt
does not affect the de-assertion timer.
SMSC LAN9312
Revision 1.2 (04-08-08)
DATA4S9HEET
SMSC [ SMSC CORPORATION ]
