Table 2-3.
Numeric Coprocessor Interface Signals
Pin
Type
Name
Description
133
Output
-BUSY
Numeric coprocessor busy status output to the
80386sx. This signal normally echoes the state of
-NPBUSY from the 80387sx. During coprocessor
error conditions, it is held low. Also, it is pulsed
repetitively by the 82C836 when no coprocessor is
present.
127
Input
-NPBUSY
Busy status from 80387sx. This signal indicates the
80387sx is currently executing a command.
128
Input
-NPERR
Error signal from the coprocessor.
Table 2-4.
Memory Interface Signals
Pin
Type
Name
Description
108-117
Output
MA0-MA9
Multiplexed DRAM address bits MA 0 to 9 are
outputs to the DRAMs
107-104
Output
-RAS<0:3>,
(MA10)
Row Address Strobes 0 to 3 are active-low strobes
used as RAS controls for the banks of DRAM. Each
bank is 18 bits wide (including 2 bits for parity).
Each byte is addressed with an even or odd CAS
signal. -RAS<0:3>, perform different functions in
an encoded RAS mode. When using a 4MB DRAM
configuration, -RAS3 becomes MA10. For further
details, refer to
Section 5, System Interface
, subsection
titled
DRAM Interface
.
101
Output
-CASH
Column Address Strobe High is an active-low output
to all high (odd) byte DRAMs.
100
Output
-CASL
Column Address Strobe Low is an active-low output
to all low (even) byte DRAMs.
119
Bidirectional
PARH
Parity High is the parity bit from the high-order bytes
of the DRAMs.
118
Bidirectional
PARL
Parity Low is the parity bit from the low-order bytes
of the DRAMs.
103
Output
-MWE
Memory Write Enable is an active-low output
connected to all DRAMs. -MWE is normally low, but
is high for read cycle. This signal can also be used
directly to control the direction of the transceivers (if
present) that buffer the DRAM data to or from the
CPU local data bus.
38
Output
-ROMCS
ROM Chip Select is an active-low output to the
EPROM(s). -ROMCS becomes active for the
progammed address range.
Pin Assignments
Signal Descriptions
I
Chips and Technologies, Inc.
P R E L I M I N A R Y
Revision 3.0
2-5