Table 3, Table 4, Table 5 – Cypress CY7C138 User Manual
Page 14
CY7C138, CY7C139
Document #: 38-06037 Rev. *D
Page 14 of 17
Table 3. Non-Contending Read/Write
Inputs
Outputs
Operation
CE
R/W
OE
SEM
I/O
0-7/8
H
X
X
H
High Z
Power-Down
H
H
L
L
Data Out
Read Data in Semaphore
X
X
H
X
High Z
I/O Lines Disabled
H
X
L
Data In
Write to Semaphore
L
H
L
H
Data Out
Read
L
L
X
H
Data In
Write
L
X
X
L
Illegal Condition
Table 4. Interrupt Operation Example (assumes BUSY
L
=BUSY
R
=HIGH)
Left Port
Right Port
Function
R/W
CE
OE
A
0-11
INT
R/W
CE
OE
A
0-11
INT
Set Left INT
X
X
X
X
L
L
L
X
FFE
X
Reset Left INT
X
L
L
FFE
H
X
X
X
X
X
Set Right INT
L
L
X
FFF
X
X
X
X
X
L
Reset Right INT
X
X
X
X
X
X
L
L
FFF
H
Table 5. Semaphore Operation Example
Function
I/O
0-7/8
Left
I/O
0-7/8
Right
Status
No action
1
1
Semaphore free
Left port writes semaphore
0
1
Left port obtains semaphore
Right port writes 0 to semaphore
0
1
Right side is denied access
Left port writes 1 to semaphore
1
0
Right port is granted access to semaphore
Left port writes 0 to semaphore
1
0
No change. Left port is denied access
Right port writes 1 to semaphore
0
1
Left port obtains semaphore
Left port writes 1 to semaphore
1
1
No port accessing semaphore address
Right port writes 0 to semaphore
1
0
Right port obtains semaphore
Right port writes 1 to semaphore
1
1
No port accessing semaphore
Left port writes 0 to semaphore
0
1
Left port obtains semaphore
Left port writes 1 to semaphore
1
1
No port accessing semaphore