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80960KB-25

EMBEDDED 32-BIT MICROPROCESSOR WITH INTEGRATED FLOATING-POINT UNIT

Intel 

80960KB

Table 5. 80960KB Pin Description: Support Signals (Sheet 2 of 2)

NAME

TYPE

DESCRIPTION

FAILURE

O

O.D.

INITIALIZATION FAILURE indicates that the processor did not initialize correctly.

After RESET deasserts and before the first bus transaction begins, FAILURE

asserts while the processor performs a self-test. If the self-test completes

successfully, then FAILURE deasserts. The processor then performs a zero

checksum on the first eight words of memory. If it fails, FAILURE asserts for a

second time and remains asserted. If it passes, system initialization continues

and FAILURE remains deasserted.

IAC/INT0

I

INTERAGENT COMMUNICATION REQUEST/INTERRUPT 0 indicates an IAC

message or an interrupt is pending. The bus interrupt control register determines

how the signal is interpreted. To signal an interrupt or IAC request in a

synchronous system, this pin — as well as the other interrupt pins — must be

enabled by being deasserted for at least one bus cycle and then asserted for at

least one additional bus cycle. In an asynchronous system the pin must remain

deasserted for at least two bus cycles and then asserted for at least two more bus

cycles.

During system reset, this signal must be in the logic high condition to enable

normal processor operation. The logic low condition is reserved.

INT1

INT2/INTR

I

INTERRUPT 1, like INT0, provides direct interrupt signaling.

I

INTERRUPT2/INTERRUPT REQUEST: The interrupt control register determines

how this pin is interpreted. If INT2, it has the same interpretation as the INT0 and

INT1 pins. If INTR, it is used to receive an interrupt request from an external

interrupt controller.

INT3/INTA

N.C.

I/O

O.D.

N/A

INTERRUPT3/INTERRUPT ACKNOWLEDGE: The bus interrupt control register

determines how this pin is interpreted. If INT3, it has the same interpretation as

the INT0, INT1 and INT2 pins. If INTA, it is used as an output to control

interrupt-acknowledge transactions. The INTA output is latched on-chip and

remains valid during Td cycles; as an output, it is open-drain.

NOT CONNECTED indicates pins should not be connected. Never connect any

pin marked N.C. as these pins may be reserved for factory use.

I/O = Input/Output, O = Output, I = Input, O.D. = Open Drain, T.S. = Three-state

2.0 ELECTRICAL SPECIFICATIONS

2.1 Power and Grounding

The 80960KB is implemented in CHMOS IV

technology and therefore has modest power require-

ments. Its high clock frequency and numerous

output buffers (address/data, control, error and

arbitration signals) can cause power surges as

multiple output buffers simultaneously drive new

signal levels. For clean on-chip power distribution,

VCC and VSS pins separately feed the device’s

functional units. Power and ground connections

must be made to all 80960KB power and ground

pins. On the circuit board, all Vcc pins must be

strapped closely together, preferably on a power

plane; all Vss pins should be strapped together,

preferably on a ground plane.

2.2 Power Decoupling

Recommendations

Place a liberal amount of decoupling capacitance

near the 80960KB. When driving the L-bus the

processor can cause transient power surges, partic-

ularly when connected to a large capacitive load.

10

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