CY7C025E Просмотр технического описания (PDF) - Cypress Semiconductor
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CY7C025E Datasheet PDF : 22 Pages
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CY7C024E, CY7C0241E
CY7C025E, CY7C0251E
When writing to the semaphore, only I/O0 is used. If a zero is
written to the left port of an available semaphore, a one appears
at the same semaphore address on the right port. That
semaphore can now only be modified by the side showing zero
(the left port in this case). If the left port now relinquishes control
by writing a one to the semaphore, the semaphore is set to one
for both sides. However, if the right port had requested the
semaphore (written a zero) while the left port had control, the
right port immediately owns the semaphore as soon as the left
port releases it. Table 3 on page 8 shows sample semaphore
operations.
When reading a semaphore, all 16/18 data lines output the
semaphore value. The read value is latched in an output register
to prevent the semaphore from changing state during a write
from the other port. If both ports attempt to access the
semaphore within tSPS of each other, the semaphore is definitely
obtained by one side or the other, but there is no guarantee which
side controls the semaphore.
Table 1. Non-Contending Read/Write
Inputs
CE R/W OE UB
LB
H
X
X
X
X
X
X
X
H
H
L
L
X
L
H
L
L
X
H
L
L
L
X
L
L
L
H
L
L
H
L
H
L
H
L
L
H
L
L
L
X
X
H
X
X
H
H
L
X
X
X
H
L
H
H
H
X
X
X
X
X
H
H
L
X
X
L
X
L
X
X
X
L
SEM
H
H
H
H
H
H
H
H
X
L
L
L
Outputs
I/O0–I/O7[9]
I/O8–I/O15[10]
High Z
High Z
High Z
High Z
High Z
Data in
Data in
High Z
Data in
Data in
High Z
Data out
Data out
High Z
Data out
Data out
High Z
High Z
Data out
Data out
Data out
Data out
Data in
Data in
L Data in
Data in
L
L
Operation
Deselected: power-down
Deselected: power-down
Write to upper byte only
Write to lower byte only
Write to both bytes
Read upper byte only
Read lower byte only
Read both bytes
Outputs disabled
Read data in semaphore flag
Read data in semaphore flag
Write DIN0 into semaphore flag
Write DIN0 into semaphore flag
Not allowed
Not allowed
Notes
9. I/O0 –I/O8 on the CY7C0241E/CY7C0251E.
10. I/O9 –I/O17 on the CY7C0241E/CY7C0251E.
Document Number: 001-62932 Rev. *B
Page 7 of 22
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