MC68882FN25A Datasheet, PDF (15/26 Pages) Freescale Semiconductor, Inc – HCMOS Enhanced Floating-Point Coprocessor

Freescale Semiconductor, Inc.
D31) when the MC68882 is configured to operate over an
8-bit data bus (i.e., connect DO to D8, D16 and D24; DI
to D9, D17, and D25; . . . and D7 to D15, D23 and D31).
The DSACK pins of the two devices are directly con-
netted, although it is not necessary to connect the DSACKI
pin since the MC68882 never asserts it in this configu-
ration.
MC68882-MC68000/MC68008/MC68010
INTERFACING
The following paragraphs describe how to connect the
MC68882 to an MC68000, MC68008, or MC6801 O proces-
sor for opertion as a peripheral via an 8- or 16-bit data
bus.
When connected as a peripheral processor, the MC68882
chip select (CS) decode, is system dependent. If the
MC68000 is used as the main processor, the MC68882 CS
must be decoded in the supervisor or user data spaces,
However, if the MC68010 is used for the main processor,
the MOVES instruction may be used to emulate any CPU
space access that the MC68020/MC68030 generates for
coprocessor communications. Thus, the CS decode logic
for such systems may be the same as in an MC68020/
MC68030 system, such that the MC68882
part of the data address spaces.
will n.o,;kt*-}s’;h.<.ts.:N:e\~*.&a. ny
,* ^{~~,,.i$#i$:,*,,{.~~:$;~”~:‘,,”.:}
8-Bit Data Bus Peripheral Processor C,~~~f~8n
16-Bit Data BUS Peripheral Processor Connection
Figure 14 illustrates the connection of an MC68882 to
an MC68000 or MC68010 as a peripheral processor over
a 16-bit data bus. The MC68882 is configured to operate
over a 16-bit data bus when the SIZE pin is connected to
Vcc, and the AO pin is connected to GND. The sixteen
least-significant data pins (DO-DI 5) must be connected to
the sixteen most-significant data pins (D16-D31 ) when the
MC68882 is configured to operate over a 16-bit data bus
(i.e., connect DO to D16, DI to D17, ,.. and D15 to D31).
The DSACKI pin of the MC68882 is connected to the
DTACK pin of the main processor, and the DSACKO pin
is not used.
Figure 15 illustrates the connecti,~hjd~j~k MC68882 to
an MC68008 as a peripheral proc<~.$~@1, _{.!g’’!r*,,,@*),ver} an 8-bit data
bus, The MC68882 is configur~ tm~perate over an 8-bit
data bus when the SIZE piq,,is’”&&#nected to GND. The
eight least-significant d~ti$~~s (DO-D7) must be con-
netted to the twenty:f~~~~~st-sig nificant pins (D8-D31 )
when the MC68882a{,~.~~b@figured to operate over an 8-
bit data bus (i,e,, q~@M’DO to D8, D16, and D24; DI to
D9, D17, and ~$; .’!:,* and D7 to D15, D23, and D31), The
DSACKO pin$$,~~~ MC68882 is connected to the DTACK
pin of th@<W~m08, and the DSACKI pin is not used.
Wh~@ ~-cted
as a peripheral processor, the MC68882
chip #&#ct (CS) decode is system dependent, and the CS
~-#s,t“, be:tiecoded in the supervisor or user data spaces.
1
r
[.;\,
i‘“:.w;$4)
1
MAIN PROCESSOR
CLOCK
I
COPROCESSOR
CLOCK
Figure 14. 16-Bit Data Bus Peripheral
Processor Connection
q
FCO-FC2 --+
CHIP
SELECT
A16-A19 --+
DECDDE _-
E
A13-A15 --*
(SYSTEM
A5-A12 -–*
DEPENDENT)
,,
Al -A4
AO ~
g
~
m
B~
:
m
R~ .
GND+
SIZE
> Al -A4
AO
g
g
E
8
+E
z
. _{- R~}
00-07 4
+ D24-D31
* D16-D23
* D8-D15
* DO-D7
DTACK ~
DSACKO
— DSACK1
f
M’AIN PRbCESSOR
CLOCK
t
COPROCESSOR
CLOCK
Figure 15. 8-Bit Data Bus Peripheral
Processor Connection
M C688B2
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BRW/Rev. 3
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