STPCD01 STMicroelectronics, STPCD01 Datasheet - Page 17

• Manufacturer Part Number: STPCD01
• Description: STPC CLIENT DATASHEET - PC COMPATIBLE EMBEDED MICROPROCESSOR
• Manufacturer: STMicroelectronics

LA[22]/SCS1# Unlatched Address (ISA) / Sec-
ondary Chip Select (IDE) This pin has two func-
tions, depending on whether the ISA bus is active
or the IDE bus is active.
When the ISA bus is active, this pin is ISA bus un-
latched address bit 22 for 16-bit devices. When
ISA bus is accessed by any cycle initiated from
PCI bus, this pin is in output mode. When an ISA
bus master owns the bus, this pin is in input mode.
When the IDE bus is active, this signal is used as
the active high secondary slave IDE chip select
signal. This signal is to be externally ANDed with
the ISAOE
to guarantee it is active only when ISA bus is idle.
LA[21]/PCS3# Unlatched Address (ISA) / Primary
Chip Select (IDE). This pin has two functions, de-
pending on whether the ISA bus is active or the
IDE bus is active.
When the ISA bus is active, this pin is ISA Bus un-
latched address bit 21 for 16-bit devices. When
ISA bus is accessed by any cycle initiated from
PCI bus, this pin is in output mode. When an ISA
bus master owns the bus, this pin is in input mode.
When the IDE bus is active, this signas is used as
the active high primary slave IDE chip select sig-
nal. This signal is to be externally NANDed with
the ISAOE
to guarantee it is active only when ISA bus is idle.
LA[20]/PCS1# Unlatched Address (ISA) / Primary
Chip Select (IDE). This pin has two functions, de-
pending on whether the ISA bus is active or the
IDE bus is active.
When the ISA bus is active, this pin is ISA Bus un-
latched address bit 20 for 16-bit devices. When
the ISA bus is accessed by any cycle initiated from
PCI bus, this pin is in output mode. When an ISA
bus master owns the bus, this pin is in input mode.
When the IDE bus is active, this signals is used as
the active high primary slave IDE chip select sig-
nal. This signal is to be externally NANDed with
the ISAOE
to guarantee it is active only when ISA bus is idle.
LA[19:17]/DA[2:0] Unlatched Address (ISA) / Ad-
dress (IDE). These pins are multi-function pins.
They are used as the ISA bus unlatched address
bits [19:17] for ISA bus or the three address bits
for the IDE bus devices.
When used by the ISA bus, these pins are ISA bus
unlatched address bits 19-17 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.
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#
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signal before driving the IDE devices
signal before driving the IDE devices
signal before driving the IDE devices
Issue 2.2 - October 13, 2000
For IDE devices, these signals are used as the
DA[2:0] and are connected directly or through a
buffer to DA[2:0] of the IDE devices. If the toggling
of signals are to be masked during ISA bus cycles,
they can be externally ORed before being con-
nected to the IDE devices.
SA[19:8]/DD[11:0] Unlatched Address (ISA) /
Data Bus (IDE). These are multifunction pins.
When the ISA bus is active, they are used as the
ISA bus system address bits 19-8. When the IDE
bus is active, they serve as IDE signals DD[11:0].
These pins are used as an input when an ISA bus
master owns the bus and are outputs at all other
times.
IDE devices are connected to SA[19:8] directly
and the ISA bus is connected to these pins
through two LS245 transceivers. The transceiver
OEs are connected to ISAOE
nected to MASTER
are connected to the CPC and IDE DD busses
and B bus signals are connected to ISA SA bus.
DD[15:12] Databus (IDE). The high 4 bits of the
IDE databus are combined with several of the X-
bus lines. Refer to the following section for X-bus
pins for further information.
SA[7:0] ISA Bus address bits [7:0]. These are the
8 low bits of the system address bus of ISA on 8-
bit slot. 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 pins are the
external databus to the ISA bus.
2.2.7.
IOCHRDY/DIORDY Channel Ready (ISA) / Busy /
Ready (IDE). This is a multi-function pin. When
the ISA bus is active, this pin is IOCHRDY. When
the IDE bus is active, this serves as IDE signal DI-
ORDY.
IOCHRDY is the I/O channel ready signal of the
ISA bus and is driven as an output in response to
an ISA master cycle targeted to the host bus or an
internal register of the STPC Client. The STPC
Client monitors this signal as an input when per-
forming 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 Client since
the access to the system memory can be consid-
erably delayed due to CRT refresh or a write back
cycle.
ISA/IDE COMBINED CONTROL
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. The transceiver bus signals
PIN DESCRIPTION
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and the DIR is con-
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