Cypress CY7C145, CY7C144 manual Non-Contending Read/Write Inputs Outputs, Operation

CY7C145, CY7C144

Table 3. Non-Contending Read/Write

Inputs

Outputs

CE

R/W

OE

SEM

I/O0−7/8

Operation

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

L =

R = HIGH)

BUSY

BUSY

Function

Left Port

Right Port

R/W

CE

OE

A0−12

INT

R/W

CE

OE

A0−12

INT

Set Left

X

X

X

X

L

L

L

X

1FFE

X

INT

Reset Left

X

L

L

1FFE

H

X

L

L

X

X

INT

Set Right

L

L

X

1FFF

X

X

X

X

X

L

INT

Reset Right

X

X

X

X

X

X

L

L

1FFF

H

INT

Table 5. Semaphore Operation Example

Function	I/O0-7/8Left	I/O0-7/8Right	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

Document #: 38-06034 Rev. *D Page 15 of 21

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