7005S55PFG Datasheet, PDF (16/21 Pages) Integrated Device Technology – HIGH-SPEED 8K x 8 DUAL-PORT STATIC RAM

IDT7005S/L
High-Speed 8K x 8 Dual-Port Static RAM
Military, Industrial and Commercial Temperature Ranges
Truth Table IV — Address BUSY
Arbitration
Inputs
Outputs
CEL CER
AOL-A12L
AOR-A12R
BUSYL⁽¹⁾ BUSYR⁽¹⁾
Function
X X NO MATCH
H
H
Normal
HX
MATCH
H
H
Normal
XH
MATCH
H
H
Normal
LL
MATCH
(2)
(2)
Write Inhibit⁽³⁾
NOTES:
2738 tbl 18
1. Pins BUSYL and BUSYR are both outputs when the part is configured as a master. Both are inputs when configured as a slave. BUSYX outputs on the IDT7005 are
push-pull, not open drain outputs. On slaves the BUSYX input internally inhibits writes.
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 can not 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 V — Example of Semaphore Procurement Sequence^(1,2,3)
Functions
D0 - D7 Left
D0 - D7 Right
Status
No Action
1
1
Semaphore free
Left Port Writes "0" to Semaphore
0
1
Left port has semaphore token
Right Port Writes "0" to Semaphore
0
1
No change. Right side has no write access to semaphore
Left Port Writes "1" to Semaphore
1
0
Right port obtains semaphore token
Left Port Writes "0" to Semaphore
1
0
No change. Left port has no write access to semaphore
Right Port Writes "1" to Semaphore
0
1
Left port obtains semaphore token
Left Port Writes "1" to Semaphore
1
1
Semaphore free
Right Port Writes "0" to Semaphore
1
0
Right port has semaphore token
Right Port Writes "1" to Semaphore
1
1
Semaphore free
Left Port Writes "0" to Semaphore
0
1
Left port has semaphore token
Left Port Writes "1" to Semaphore
1
1
Semaphore free
NOTES:
1. This table denotes a sequence of events for only one of the eight semaphores on the IDT7005.
2. There are eight semaphore flags written to via I/O0 and read from all I/O's. These eight semaphores are addressed by A0 - A2.
3. CE=VIH, SEM=VIL to access the semaphores. Refer to the semaphore Read/Write Control Truth Table.
2738 tbl 19
Functional Description
The IDT7005 provides two ports with separate control, address and
I/O pins that permit independent access for reads or writes to any location
in memory. The IDT7005 has an automatic power down feature controlled
by CE. The CE controls on-chip power down circuitry that permits the
respective port to go into a standby mode when not selected (CE HIGH).
When a port is enabled, access to the entire memory array is permitted.
Interrupts
If the user chooses the interrupt function, a memory location (mail box
or message center) is assigned to each port. The left port interrupt flag
(INTL) is asserted when the right port writes to memory location 1FFE
(HEX), where a write is defined as CE = R/W= VIL per Truth Table III.
The left port clears the interrupt through access of address location 1FFE
when CE = OE = VIL. For this example, R/W is a "don't care". Likewise,
the right port interrupt flag (INTR) is asserted when the left port writes to
memory location 1FFF (HEX) and to clear the interrupt flag (INTR), the
right port must read the memory location 1FFF. The message (8 bits) at
1FFE or 1FFF is user-defined, since it is an addressable SRAM location.
If the interrupt function is not used, address locations 1FFE and 1FFF are
not used as mail boxes, but as part of the random access memory. Refer
to Truth Table III for the interrupt operation.
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