IDT7025S/L
High-Speed 8K x 16 Dual-Port Static RAM
Military, Industrial and Commercial Temperature Ranges
Truth Table II — Address BUSY
Arbitration
Inputs
Outputs
A
0L-A12L
(1)
(1)
A
0R-A12R
Function
Normal
Normal
Normal
CE
L
CE
R
BUSY
L
BUSYR
X
H
X
L
X
X
H
L
NO MATCH
MATCH
H
H
H
H
MATCH
H
H
MATCH
(2)
(2)
Write Inhibit(3)
2683 tbl 17
NOTES:
1. Pins BUSYL and BUSYR are both outputs when the part is configured as a master. BUSY are inputs when configured as a slave. BUSYx outputs on the IDT7025
are push pull, not open drain outputs. On slaves the BUSY asserted internally inhibits write.
2. "L" if the inputs to the opposite port were stable prior to the address and enable inputs of this port. "H" if the inputs to the opposite port became stable after the address
and enable inputs of this port. If tAPS is not met, either BUSYL or BUSYR = LOW will result. BUSYL and BUSYR outputs cannot be LOW simultaneously.
3. Writes to the left port are internally ignored when BUSYL outputs are driving LOW regardless of actual logic level on the pin. Writes to the right port are internally ignored
when BUSYR outputs are driving LOW regardless of actual logic level on the pin.
Truth Table III — Example of Semaphore Procurement Sequence(1,2,3)
Functions
D0
- D15 Left
D0
- D15 Right
Status
No Action
1
0
0
1
1
0
1
1
1
0
1
1
1
1
0
0
1
1
0
1
1
1
Semaphore free
Left Port Writes "0" to Semaphore
Right Port Writes "0" to Semaphore
Left Port Writes "1" to Semaphore
Left Port Writes "0" to Semaphore
Right Port Writes "1" to Semaphore
Left Port Writes "1" to Semaphore
Right Port Writes "0" to Semaphore
Right Port Writes "1" to Semaphore
Left Port Writes "0" to Semaphore
Left Port Writes "1" to Semaphore
Left port has semaphore token
No change. Right side has no write access to semaphore
Right port obtains semaphore token
No change. Left port has no write access to semaphore
Left port obtains semaphore token
Semaphore free
Right port has semaphore token
Semaphore free
Left port has semaphore token
Semaphore free
2683 tbl 18
NOTES:
1. This table denotes a sequence of events for only one of the eight semaphores on the IDT7025.
2. There are eight semaphore flags written to via I/O0 and read from all I/0's. These eight semaphores are addressed by A0 - A2.
3. CE = VIH, SEM = VIL, to access the semaphores. Refer to the Semaphore Read/Write Truth Table.
FunctionalDescription
(HEX),whereawriteisdefinedastheCER =R/WR=VIL perTruthTable
I. The left port clears the interrupt by an address location 1FFE access
when CEL = OEL = VIL, R/WL is a "don't care". Likewise, the right port
interruptflag(INTR)isassertedwhentheleftportwritestomemorylocation
1FFF(HEX)andtocleartheinterruptflag(INTR),therightportmustaccess
the memory location 1FFF, The message (16 bits) at 1FFE or 1FFF is
user-defined, since it is an addressable SRAM location. If the interrupt
functionisnotused, addresslocations1FFEand1FFFarenotusedas
mailboxes,butaspartoftherandomaccessmemory.RefertoTruthTable
Ifortheinterruptoperation.
TheIDT7025providestwoportswithseparatecontrol,addressand
I/Opinsthatpermitindependentaccessforreadsorwritestoanylocation
inmemory.TheIDT7025hasanautomaticpowerdownfeaturecontrolled
by CE. The CE controls on-chip power down circuitry that permits the
respectiveporttogointoastandbymodewhennotselected(CE=VIH).
Whenaportisenabled,accesstotheentirememoryarrayispermitted.
Interrupts
Iftheuserchoosestheinterruptfunction,amemorylocation(mailbox
ormessagecenter)isassignedtoeachport. Theleftportinterruptflag
(INTL) is asserted when the right port writes to memory location 1FFE
6.1482
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