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CY7C024/0241
CY7C025/0251
Document #: 38-06035 Rev. *B
Page 16 of 20
Table 1. Non-Contending Read/Write
Inputs
Outputs
CE
R/W
OE
UB
LB
SEM
I/O0–I/O7
[2]
I/O8–I/O15
[3]
Operation
H
X
X
X
X
H
High Z
High Z
Deselected: Power-Down
X
X
X
H
H
H
High Z
High Z
Deselected: Power-Down
L
L
X
L
H
H
High Z
Data In
Write to Upper Byte Only
L
L
X
H
L
H
Data In
High Z
Write to Lower Byte Only
L
L
X
L
L
H
Data In
Data In
Write to Both Bytes
L
H
L
L
H
H
High Z
Data Out
Read Upper Byte Only
L
H
L
H
L
H
Data Out
High Z
Read Lower Byte Only
L
H
L
L
L
H
Data Out
Data Out
Read Both Bytes
X
X
H
X
X
X
High Z
High Z
Outputs Disabled
H
H
L
X
X
L
Data Out
Data Out
Read Data in Semaphore Flag
X
H
L
H
H
L
Data Out
Data Out
Read Data in Semaphore Flag
H
X
X
X
L
Data In
Data In
Write DIN0 into Semaphore Flag
X
X
H
H
L
Data In
Data In
Write DIN0 into Semaphore Flag
L
X
X
L
X
L
Not Allowed
L
X
X
X
L
L
Not Allowed
Table 2. Interrupt Operation Example (assumes BUSYL=BUSYR=HIGH)
[41]
Left Port
Right Port
Function
R/WL
CEL
OEL
A0L–11L
INTL
R/WR
CER
OER
A0R–11R
INTR
Set Right INTR Flag
L
L
X
(1)FFF
X
X
X
X
X
L[43]
Reset Right INTR Flag
X
X
X
X
X
X
L
L
(1)FFF
H[42]
Set Left INTL Flag
X
X
X
X
L[42]
L
L
X
(1)FFE
X
Reset Left INTL Flag
X
L
L
(1)FFE
H[43]
X
X
X
X
X
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