376 Datasheet, PDF (58/95 Pages) Intel Corporation – 376TM HIGH PERFORMANCE 32-BIT EMBEDDED PROCESSOR

376 EMBEDDED PROCESSOR
4 5 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
4 6 Component and Revision
Identifiers
To assist 80376 users the 80376 after reset holds a
component identifier and revision identifier in its DX
register The upper 8 bits of DX hold 33H as identifi-
cation of the 80376 component (The lower nibble
03H refers to the Intel386^TM 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 4 7 Component and
Revision Identifier History
80376 Stepping Name
A0
B
Revision Identifier
05H
08H
4 7 Coprocessor Interfacing
The 80376 provides an automatic interface for the
Intel 80387SX numeric floating-point coprocessor
The 80387SX coprocessor uses an I O 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 I O-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 I O-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 I O-mapped protection of
the interface can be provided with the 80376 IOPL
(I O Privilege Level) mechanism
The 80387SX numeric coprocessor interface is I O
mapped as shown in Table 4 8 Note that the
80387SX coprocessor interface addresses are be-
yond the 0H-0FFFFH range for programmed I O
When the 80376 supports the 80387SX coproces-
sor the 80376 automatically generates bus cycles to
the coprocessor interface addresses
Table 4 8 Numeric Coprocessor Port Addresses
Address in 80376
I O Space
8000F8H
8000FCH
8000FEH
80387SX
Coprocessor Register
Opcode Register
Operand Register
Operand Register
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