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