376 datasheet(58/95 Pages) INTEL

58 / 95 page

376 EMBEDDED PROCESSOR

45 Self-Test Signature

Upon completion of self-test (if self-test was re-

quested by driving BUSY LOW at the falling edge of

RESET) the EAX register will contain a signature of

00000000H indicating the 80376 passed its self-test

of microcode and major PLA contents with no prob-

lems detected

The passing signature in EAX

00000000H applies to all 80376 revision levels Any

non-zero signature indicates the 80376 unit is faulty

46 Component and Revision

Identifiers

To assist 80376 users the 80376 after reset holds a

component identifier and revision identifier in its DX

cation of the 80376 component (The lower nibble

03H refers to the Intel386TM architecture The up-

per nibble 30H refers to the third member of the

Intel386 family) The lower 8 bits of DX hold an

8-bit unsigned binary number related to the compo-

nent revision level The revision identifier will in gen-

eral chronologically track those component step-

pings which are intended to have certain improve-

ments or distinction from previous steppings The

80376 revision identifier will track that of the 80386

where possible

The revision identifier is intended to assist 80376

users to a practical extent However the revision

identifier value is not guaranteed to change with ev-

ery stepping revision or to follow a completely uni-

form numerical sequence depending on the type or

intention of revision or manufacturing materials re-

quired to be changed Intel has sole discretion over

these characteristics of the component

Table 47 Component and

Revision Identifier History

80376 Stepping Name

Revision Identifier

05H

08H

47 Coprocessor Interfacing

The 80376 provides an automatic interface for the

Intel 80387SX numeric floating-point coprocessor

The 80387SX coprocessor uses an IO mapped in-

terface driven automatically by the 80376 and as-

sisted by three dedicated signals BUSY ERROR

and PEREQ

As the 80376 begins supporting a coprocessor in-

struction it tests the BUSY and ERROR signals to

determine if the coprocessor can accept its next in-

struction Thus the BUSY and ERROR inputs elimi-

nate the need for any ‘‘preamble’’ bus cycles for

communication between processor and coproces-

sor The 80387SX can be given its command op-

code immediately The dedicated signals provide

instruction synchronization and eliminate the need

of using the 80376 WAIT opcode (9BH) for 80387SX

instruction synchronization (the WAIT opcode was

required when the 8086 or 8088 was used with the

8087 coprocessor)

Custom coprocessors can be included in 80376

based systems by memory-mapped or IO-mapped

interfaces

Such coprocessor interfaces allow a

completely custom protocol and are not limited to a

set of coprocessor protocol ‘‘primitives’’ Instead

memory-mapped or IO-mapped interfaces may use

all applicable 80376 instructions for high-speed co-

processor communication The BUSY and ERROR

inputs of the 80376 may also be used for the custom

coprocessor interface if such hardware assist is de-

sired These signals can be tested by the 80376

WAIT opcode (9BH) The WAIT instruction will wait

until the BUSY input is inactive (interruptable by an

NMI or enabled INTR input) but generates an ex-

ception 16 fault if the ERROR pin is active when the

BUSY goes (or is) inactive If the custom coproces-

sor interface is memory-mapped protection of the

addresses used for the interface can be provided

with the segmentation mechanism of the 80376 If

the custom interface is IO-mapped protection of

the interface can be provided with the 80376 IOPL

(IO Privilege Level) mechanism

The 80387SX numeric coprocessor interface is IO

mapped as shown in Table 48

Note that the

80387SX coprocessor interface addresses are be-

yond the 0H-0FFFFH range for programmed IO

When the 80376 supports the 80387SX coproces-

sor the 80376 automatically generates bus cycles to

the coprocessor interface addresses

Table 48 Numeric Coprocessor Port Addresses

Address in 80376

80387SX

IO Space

Coprocessor Register

8000F8H

Opcode Register

8000FCH

Operand Register

8000FEH

Operand Register

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