Intel 80960SA, Руководство пользователя

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8
80960SA
Table 3. 80960SA Pin Description: Bus Signals (Sheet 1 of 2)
NAME TYPE DESCRIPTION
CLK2 I SYSTEM CLOCK provides the fundamental timing for 80960SA systems. It is
divided by two inside the 80960SA to generate the internal processor clock.
A31:16 O
T.S.
ADDRESS BUS carries the upper 16 bits of the 32-bit physical address to memory.
It is valid throughout the burst cycle; no latch is required.
AD15:1, D0 I/O
T.S.
ADDRESS/DATA BUS carries the low order 32-bit addresses and 16-bit data to
and from memory. AD15:4 must be latched since the cycle following the address
cycle carries data on the bus.
A3:1 O
T.S.
ADDRESS BUS carries the word addresses of the 32-bit address to memory.
These three bits are incremented during a burst access indicating the next word
address of the burst access. Note that A3:1 are duplicated with AD3:1 during the
address cycle.
ALE O
T.S.
ADDRESS LATCH ENABLE indicates the transfer of a physical address. ALE is
asserted during a T
a
cycle and deasserted before the beginning of the T
d
state. It is
active HIGH and floats to a high impedance state during a hold cycle (T
h
).
AS O
T.S.
ADDRESS STATUS indicates an address state. AS is asserted every T
a
state and
deasserted during the following T
d
state. AS is driven HIGH during reset.
W/R O
T.S.
WRITE/READ specifies, during a T
a
cycle, whether the operation is a write or read.
It is latched on-chip and remains valid during T
d
cycles.
DEN O
T.S.
DATA ENABLE is asserted during T
d
cycles and indicates transfer of data on the
AD lines. The AD lines should not be driven by an external source unless DEN is
asserted. When DEN is asserted, outputs from the previous cycle are guaranteed
to be three-stated. In addition, DEN deasserted indicates inputs have been
captured; therefore input hold times can be disregarded. DEN is driven HIGH
during reset.
DT/R O
T.S.
DATA TRANSMIT / RECEIVE indicates the direction of data transfer to and from
the bus. It is low during T
a
and T
d
cycles for a read or interrupt acknowledgment; it
is high during T
a
and T
d
cycles for a write. DT/R never changes state when DEN is
asserted. DT/R is driven HIGH during reset.
READY I READY indicates that data on AD lines can be sampled or removed. If READY is
not asserted during a T
d
cycle, the T
d
cycle is extended to the next cycle by
inserting a wait state (T
w
).
I/O = Input/Output, O = Output, I = Input, O.D. = Open Drain, T.S. = Three-state