Major Chips Description 2-19
Table 2-3 M1523 Signal Descriptions (continued)
Signal Pin Type Description
PCI Interrupt Unit
INTAJ_MI 67 IPCI Interrupt Input A or PCI interrupt polling input.
INTBJ 68 I/O PCI Interrupt Input B or polling select_0 output.
INTCJ 69 I/O PCI Interrupt Input C or polling select_1 output.
INTDJ 70 I/O PCI Interrupt Input D or polling select_2 output.
PCI Arbiter
PHOLDJ 66 OM1523 requests the ownership of the PCI bus.
Hardware setting option
Pull low : internal RTC is enabled
Pull high : external RTC is used.
PHLDAJ 65 IPCI Hold Acknowledge. When this pin is asserted, the
M1523 owns the PCI bus.
CPU Interface (3.3V)
IGNNEJ 55 OIgnore Numeric Error. This pin is used as the ignore
numeric coprocessor error.
INTR 54 OInterrupt Request to CPU. This is the interrupt signal
generated by the internal 8259.
NMI 58 ONon-maskable Interrupt. This is non-maskable interrupt
request to CPU.
A20MJ 56 OCPU A20 Mask. This is the address line 20 mask signal.
ISA Interface
FERRJ/IRQ13 62 IFloating Point Error. FERRJ input to generate IRQ13.
When the coprocessor interface is disabled in
configuration port 43h bit 6, the function of this pin is
IRQ13.
IRQ12 / MDATAO 155 I/O Mouse Interrupt Request Input/Mouse Data Output. When
internal PS/2 keyboard is disabled, this pin is mouse
interrupt input. Otherwise, this pin is mouse data output.
IRQ[15:14],
IRQ[11:9],
IRQ[7:3]
20, 22, 13, 11,
164, 194, 196,
200, 202
IInterrupt Request Signals.
SD[15:8] 42, 41, 39, 37,
35, 33, 31, 29 I/O ISA High-byte Slot Data Bus. These lines are system data
lines.
XD[7:0] 161-163, 165,
167, 168, 170-
171
I/O External Data Bus lines connect to SD[7:0] by an external
TTL LS245, whose direction is controlled by the M1523
output signal XDIR.
SA19 175 OISA Slot Address Bus A19.
SA18 177 OISA Slot Address Bus A18.
SA17 179 OISA Slot Address Bus A17.