NS486SXL Datasheet, PDF (11/26 Pages) National Semiconductor (TI) – Optimized 32-Bit 486-Class Controller with On-Chip Peripherals for Embedded Systems

2.0 SXL Pin Description Tables (Continued)
TABLE 7. Auxiliary Processor Interface Pins
Symbol
EREQ
EACK
DRV
Pins
52
53
54
Type
O
I
O
Function
External bus REQuest (active-low) to an auxiliary processor. This signal is
asserted whenever the auxiliary processor feature of a programmable chip select
is enabled. This is used to request access to a shared memory from another
processor.
External bus ACKnowledge (active-low) from an auxiliary processor.
Auxiliary processor shared memory DRiVe control signal. Once access is granted
to the shared memory, this signal is asserted to enable the address, data and
control signal buffers to drive the shared memory pins.
Symbol
TEST
Pins
42
TABLE 8. Test Pins
Type
I
Function
Reserved for testing and development system support. Normally pulled high. A
small number of test modes are documented for use by the customer. While
TEST is asserted, all output pins except OSCX2 and RTCX2 are TRI-STATE.
Symbol
NMI
INTA
IRQ[7:0]
Pins
55
56
46, 47, 57, 58,
59, 60, 61, 62
TABLE 9. Interrupt Control Pins
Type
I
O
I
Function
Non-Maskable Interrupt. This active-high signal will generate a non-maskable
interrupt to the CPU when it is active high. Normally this signal is used to indicate
a serious system error.
INTerrupt Acknowledge. During each interrupt acknowledge cycle this signal will
strobe low; it should be used by external cascaded interrupt controllers.
Interrupt ReQuests. These inputs are either rising edge or low-level sensitive
interrupt requests, depending on the configuration of the internal interrupt
controllers. These interrupt requests may also be programmed to support
externally cascaded interrupt controller(s). The IRQ pins are also used to select a
particular test in test mode.
Symbol
RTCX1
RTCX2
Vbat
Pins
38
40
41
TABLE 10. Real Time Clock Pins
Type
I
O
I
Function
Real Time Clock crystal oscillator input: 32 kHz crystal.
Real Time Clock crystal oscillator output: 32 kHz crystal.
External + battery input for real time clock.
Symbol
SYSCLK
OSCX1
Pins
73
22
TABLE 11. Oscillator Pins
Type
O
I
Function
SYStem CLocK. This clock output pin will either be driven with a signal half the
frequency of the OSCX1 input clock frequency or the CPU’s clock frequency,
which is determined in the Power Management Control Register 1. The source
selection for this signal is determined by bit 1 of the Power Management Control
Register 3.
OSCillator Crystal 1 input. This pin should either be driven by a TTL oscillator or
be connected to an external crystal circuit. This signal is the fundamental clock
source for all clocked elements in the NS486SXL, except the Real-Time Clock,
which has its own crystal pins.
11
www.national.com