MC68882FN25A Datasheet, PDF (14/26 Pages) Freescale Semiconductor, Inc – HCMOS Enhanced Floating-Point Coprocessor

Freescale Semiconductor, Inc.
INTERFACING METHODS
MC68882/MC6801 O OR MC68030 INTERFACING
The following paragraphs describe how to connect the
MC68882 to an MC68020 or MC68030 for coprocessor
operation via an 8-, 16-, or 32-bit data bus,
A16-A19 ~
DEcoDE I
32-Bit Data Bus Coprocessor Connection
Figure 11 illustrates the coprocessor interface connec-
tion of an MC68882 to an MC68020/MC68030 via a 32-bit
data bus. The MC68882 is configured to operate over a
32-bit data bus when both the AO and SIZE pins are con-
netted
to VCC.
a- ^FCO-FC2
A20-A31 ^—
CHIP
SELECT
E
A16-A19
OECODE
A13-A15
A5-A12 ^—
Vcc
SIZE
~
A1-A4 ~
~
AO
A1-A4
8
z
E
E
0
~
E
0
z
R~
z
D24-031
D24-D31
016-D23
D16-D23
D8-D15
D8-D15
DO-D7
DO-D?
FCO-FC2
DSACKO
DSACK1
I
v.
-
SIZE
MAIN PROCESSOR
CLOCK
./,,,:.,,,,,$:/;
16-Bit Data Bus @+@oce&sor Connection
Figure 12 ill.y~~~#’the coprocessor interface connec-
tion of an M~m2 to an MC68020/MC68030 via a 16-bit
data bu~i,~k~WC68882 is configured to operate over a
16-bit,@~d~~ bus when the SIZE pin is connected to VCC,
and. t~e ~0 pin is connected to GND. The sixteen least-
s~~k~?aridtata pins (DO-D15) must be connected to the
$:a~~~~en most-significant data pins (D1 6-D31 ) when the
!&&8882 is configured to operate over a 16-bit data bus
~.e., connect DO to D16, DI to D17, . . . and D15 to D31).
The DSACK pins of the two devices are directly con-
nected, although it is not necessary to connect the DSACKO
pin since the MC68882 never asserts it in this configu-
ration.
8-Bit Data Bus Coprocessor Connection
Figure 13 illustrates the connect of an MC68882 to an
MC68020/MC68030 as a coprocessor over an 8-bit data
D24-D31
D16-D23
08-015
DO-D7 _m
=H
J
+
MAIN PROCESSOR
CLOCK
D24-D31
D16-D23
Da-D15
DO-07
DSACKO
OSACK1
\
?
COPROCESSOR
CLOCK
figure 13. 8-Bit Data Bus Coprocessor Connection
bus. The MC68882 is configured to operate over an 8-bit
data bus when the SIZE pin is connected to GND. The
twenty-four least-significant data pins (DO-D23) must be
connected to the eight most-significant data pins (D24-
MOTOROU
14
,.,
For More Information On This Product,
Go to: www.freescale.com
,,
MC-
BRW/Rav. 3
. . . . ....,,,. . . .. . .. ,,. -