Programmable Interrupt Controller
15-12
Élan™SC520 Microcontroller User’s Manual
15.5.3.2
PC/AT Compatibility
For PC/AT-compatible systems, the microcontroller hardware does not automatically map
legacy ISA interrupt signals to their respective Slave 1 and Master controllers. The user’s
software must ensure that these interrupts are routed correctly to the appropriate PC/AT-
compatible channels. Table 15-4 shows the interrupt channel assignment implemented in
a PC/AT-compatible system.
15.5.3.3
Floating Point Errors
The ÉlanSC520 microcontroller supports DOS-compatible floating point error handling via
the standard Floating Point Error Interrupt Clear (FPUERRCLR) register (Port 00F0h), as
in legacy PC/AT systems. PC/AT systems control floating point error reporting externally
through the PC’s interrupt controller, rather than through the internal CPU interrupt. In this
case, an interrupt request is generated and typically routed to IRQ13 (although it is
programmable via the ÉlanSC520 microcontroller’s PIC). This allows an interrupt handler
to write to the Floating Point Error Interrupt Clear (FPUERRCLR) register to clear the
interrupt request and force the CPU’s ignore numeric error (ignne) signal active, thus
enabling execution of floating-point instructions within the interrupt handler. Once the FPU
error condition is cleared by the handler, the floating point error (ferr) signal is deasserted,
Table 15-4
PC/AT Interrupt Channel Mapping
PC/AT-Compatible System
ÉlanSC520 Microcontroller
IRQ
I/O Device
Priority
Interrupt Source to Map
IRQ0
System Timer 0
P1
Internal (PIT 0 interrupt)
IRQ1
Keyboard interface
P2
External via GPIRQx pin
IRQ2
1, 2
Notes:
1. In the ÉlanSC520 microcontroller’s PIC, interrupt channels 2 and 5 of the Master interrupt con-
troller are hard-wired to the outputs of Slave 1 and Slave 2 interrupt controllers, respectively. The
cascading of the slave controllers is fixed in order to simplify the system interrupt programming
model.
2. When configured for PC/AT-compatible operation, the Slave 1 interrupt controller is cascaded
and the Slave 2 controller is bypassed. In this configuration, IRQ2 is not available, and interrupt pri-
ority P13 acts as IRQ5. For configuration details see “PC/AT Compatibility” on page 15-12.
Slave controller cascading
—
Cascaded from Slave 1 controller
IRQ3
UART 2
P11
Internal (UART 2 interrupt)
IRQ4
UART 1
P12
Internal (UART 1 interrupt)
IRQ5
1, 2
Parallel port 2
P13
External via GPIRQx pin
IRQ6
Floppy disk controller
P21
External via GPIRQx pin
IRQ7
Parallel port 1
P22
External via GPIRQx pin
IRQ8
Real-time clock
P3
Internal (RTC interrupt)
IRQ9
Any 8- or 16-bit ISA device
P4
External via GPIRQx pin
IRQ10
Any 8- or 16-bit ISA device
P5
External via GPIRQx pin
IRQ11
Any 8- or 16-bit ISA device
P6
External via GPIRQx pin
IRQ12
Mouse interface
P7
External via GPIRQx pin
IRQ13
Numeric coprocessor
P8
Internal (floating point error interrupt)
IRQ14
Any 8- or 16-bit ISA device
P9
External via GPIRQx pin
IRQ15
Any 8- or 16-bit ISA device
P10
External via GPIRQx pin
Содержание Elan SC520
Страница 1: ...lan SC520 Microcontroller User s Manual Order 22004A...
Страница 4: ...iv lan SC520 Microcontroller User s Manual...
Страница 28: ...Introduction xxviii lan SC520 Microcontroller User s Manual...
Страница 42: ...Architectural Overview 1 14 lan SC520 Microcontroller User s Manual...
Страница 78: ...System Initialization 3 22 lan SC520 Microcontroller User s Manual...
Страница 108: ...Clock Generation and Control 5 10 lan SC520 Microcontroller User s Manual...
Страница 118: ...Reset Generation 6 10 lan SC520 Microcontroller User s Manual...
Страница 148: ...System Arbitration 8 24 lan SC520 Microcontroller User s Manual...
Страница 214: ...SDRAM Controller 10 36 lan SC520 Microcontroller User s Manual...
Страница 230: ...Write Buffer and Read Buffer 11 16 lan SC520 Microcontroller User s Manual...
Страница 288: ...GP Bus DMA Controller 14 22 lan SC520 Microcontroller User s Manual...
Страница 316: ...Programmable Interval Timer 16 8 lan SC520 Microcontroller User s Manual...
Страница 328: ...Software Timer 18 4 lan SC520 Microcontroller User s Manual...
Страница 346: ...Real Time Clock 20 12 lan SC520 Microcontroller User s Manual...
Страница 360: ...UART Serial Ports 21 14 lan SC520 Microcontroller User s Manual...
Страница 414: ...AMDebug Technology 26 8 lan SC520 Microcontroller User s Manual...