STPCI01 STMicroelectronics, STPCI01 Datasheet - Page 18

• Manufacturer Part Number: STPCI01
• Description: STPC INDUSTRIAL - PC COMPATIBLE EMBEDED MICROPROC
• Manufacturer: STMicroelectronics

PIN DESCRIPTION
CAS#[7:0] Column Address Strobe. There are 8
active low column address strobe outputs, one
each for each Byte of the memory.
The CAS# signals drive the SIMMs either directly
or through external buffers.
These pins are always outputs, but they can also
simultaneously be inputs, to allow the memory
controller to monitor the value of the CAS# signals
at the pins.
MWE# Write Enable. Write enable specifies
whether the memory access is a read (MWE# = H)
or a write (MWE# = L). This single write enable
controls all DRAMs. It can be externally buffered
to boost the maximum number of loads (DRAM
chips) supported.
The MWE# signals drive the SIMMs directly with-
out any external buffering.
2.2.4 LOCAL BUS INTERFACE
PA[21:0] Memory Address. This is the 22-bit Lo-
cal Bus Address
PD[15:0] Data Bus. This is the 16-bit bidirectional
Local Bus Data bus.
PRDY# Ready. This input signals the Local Bus
Ready state.
PWR#1 Memory and I/O Write signal for MS Byte
PWR#0 Memory and I/O Write signal for LS Byte .
PRD#1 Memory and I/O Read signals for MS
Byte .
PRD#0 Memory and I/O Read signals for LS Byte .
FCS#[1:0], IOCS#[3:0] Flash Memory and I/O
Chip select.
2.2.5 ISA BUS INTERFACE
LA[23:17] Unlatched Address. These unlatched
ISA Bus pins address bits 23-17 on 16-bit devices.
When the ISA bus is accessed by any cycle initiat-
ed from the PCI bus, these pins are in output
mode. When an ISA bus master owns the bus,
these pins are tristated.
SA[19:0] Unlatched Address. These are the 20
low bits of the system address bus of ISA. These
pins are used as an input when an ISA bus master
owns the bus and are outputs at all other times.
SD[15:0] I/O Data Bus (ISA). These are the exter-
nal ISA data bus pins.
IOCHRDY IO Channel Ready. IOCHRDY is the IO
channel ready signal of the ISA bus and is driven
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(Combined with ISA Bus)
Issue 2.4 - February 11, 2002
as an output in response to an ISA master cycle
targeted to the host bus or an internal register of
the STPC Industrial. The STPC Industrial moni-
tors this signal as an input when performing an
ISA cycle on behalf of the host CPU, DMA master
or refresh.
ISA masters which do not monitor IOCHRDY are
not guaranteed to work with the STPC Industrial
since the access to the system memory can be
considerably delayed due to CRT refresh or a
write back cycle.
ALE Address Latch Enable. This is the address
latch enable output of the ISA bus and is asserted
by the STPC Industrial to indicate that LA23-17,
SA19-0, AEN and SBHE# signals are valid. The
ALE is driven high during refresh, DMA master or
an ISA master cycles by the STPC Industrial.
ALE is driven low after reset.
BHE# System Bus High Enable. This signal, when
asserted, indicates that a data Byte is being trans-
ferred on SD15-8 lines. It is used as an input when
an ISA master owns the bus and is an output at all
other times.
MEMR# Memory Read. This is the memory read
command signal of the ISA bus. It is used as an in-
put when an ISA master owns the bus and is an
output at all other times.
The MEMR# signal is active during refresh.
MEMW# Memory Write. This is the memory write
command signal of the ISA bus. It is used as an in-
put when an ISA master owns the bus and is an
output at all other times.
SMEMR# System Memory Read. The STPC In-
dustrial generates SMEMR# signal of the ISA bus
only when the address is below one MByte or the
cycle is a refresh cycle.
SMEMW# System Memory Write. The STPC In-
dustrial generates SMEMW# signal of the ISA bus
only when the address is below one MByte.
IOR# I/O Read. This is the IO read command sig-
nal of the ISA bus. It is an input when an ISA mas-
ter owns the bus and is an output at all other
times.
IOW# I/O Write. This is the IO write command sig-
nal of the ISA bus. It is an input when an ISA mas-
ter owns the bus and is an output at all other
times.
MASTER# Add On Card Owns Bus. This signal is
active when an ISA device has been granted bus
ownership.
MCS16# Memory Chip Select16. This is the de-
code of LA23-17 address pins of the ISA address