IDT72T51336 ETC-unknow, IDT72T51336 Datasheet - Page 20

• Manufacturer Part Number: IDT72T51336
• Description: 2.5v Multi-queue Flow-control Devices 8 Queues 36 Bit Wide Configuration 589,824 Bits, 1,179,648 Bits And 2,359,296 Bits
• Manufacturer: ETC-unknow

READ QUEUE SELECTION AND READ OPERATION
(STANDARD MODE)
can be configured up to a maximum of 8 queues which data can be read via
a common read port using the data outputs (Qout), read clock (RCLK) and read
enable (REN). An output enable, OE control pin is also provided to allow High-
Impedance selection of the Qout data outputs. The multi-queue device read port
operates in a mode similar to “First Word Fall Through” on a SuperSync IDT
FIFO, but with the added feature of data output pipelining (see Figure 11, Write
Operations & First Word Fall Through). The queue to be read is selected by
the address presented on the read address bus (RDADD) during a rising edge
on RCLK while read address enable (RADEN) is HIGH. The state of REN does
not impact the queue selection. The queue selection requires 1 RCLK cycles.
All subsequent data reads will be from this queue until another queue is selected.
device as opposed to Packet Mode where complete packets may be read. The
read port is designed such that 100% bus utilization can be obtained. This means
that data can be read out of the device on every RCLK rising edge including
the cycle that a new queue is being addressed.
(see Figure 13, Read Queue Select, Read Operation). RADEN goes high
signaling a change of queue (clock cycle “D”). The address on RDADD at that
time determines the next queue. Data presented during that cycle (“D”) will be
read at “D” (+ t
(old) queue (Q
these two clock cycles, data will not be read from the previous queue. The next
cycle’s rising edge (“F”), the read port discrete empty flag will update to show
the empty status of the newly selected queue (Q
loaded at this time (“F”) with the last word from the previous (old) queue (Q
TABLE 2 — READ ADDRESS BUS, RDADD[5:0]
IDT72T51336/72T51346/72T51356 2.5V, MULTI-QUEUE FLOW-CONTROL DEVICES
(8 QUEUES) 36 BIT WIDE CONFIGURATION 589,824, 1,179,648 and 2,359,296 bits
The IDT72T51336/72T51346/72T51356 multi-queue flow-control devices
Standard mode operation is defined as individual words will be read from the
Changing queues requires a minimum of three RCLK cycles on the read port
A
), and the next cycle (“E”), can continue to be read from the active
P
), provided REN is active LOW. If REN is HIGH (inactive) for
Flag Bus device
Read Queue
PAEn/PRn
Null Queue
Operation RCLK
Select
Select
Select
F
). The internal pipeline is also
RADEN
1
0
1
ESTR
0
1
0
F
)
20
as well as the next word from the new queue (Q
through to the output register (provided the OE is asserted) consecutively
(cycles “F” and “G” respectively) following the selection of the new queue
regardless of the state of REN, unless the new queue (Q
selected queue is empty, any reads from that queue will be prevented. Data
cannot be read from an empty queue. The last word in the data output register
(from the previous queue), will remain on the data bus, but the output valid flag,
OV will go HIGH, to indicate that the data present is no longer valid. This pipelining
effect provides the user with 100% bus utilization, and brings about the possibility
that a “NULL” queue may be required within a multi-queue device. Null queue
operation is discussed in the next section. Remember that OE allows the user
to place the data output bus (Qout) into High-Impedance and the data can be
read in to the output register regardless of OE.
13, 15, and 16 for read queue selection and read port operation timing diagrams.
PACKET MODE OPERATION (PKT = HIGH on Master Reset)
packets or frames can be written to the device as opposed to Standard mode
where individual words are written. For clarification, in Packet Mode, a packet
can be written to the device with the starting location designated as Transmit Start
of Packet (TSOP) and the ending location designated as Transmit End of Packet
(TEOP). In conjunction, a packet read from the device will be designated as
Receive Start of Packet (RSOP) and a Receive End of Packet (REOP). The
minimum size for a packet is four words (SOP, two words of data and EOP). The
almost empty flag bus becomes the “Packet Ready” PR flag bus when the device
is configured for packet mode. Valid packets are indicated when both PR and
OV are asserted.
Refer to Table 2, for Read Address Bus arrangement. Also, refer to Figures
The Packet mode operation provides the capability where, user defined
Null-Q
0
0
1
Device Select
(Compared to
ID0,1,2)
Device Select
(Compared to
ID0,1,2)
5 4 3
5 4 3
5 4 3
X
X
RDADD[5:0]
X
Read Queue Address
(3 bits = 8 Queues)
X
2
2
2
X
COMMERCIAL AND INDUSTRIAL
X
1 0
1 0
1 0
X
X
X
6114 drw06
TEMPERATURE RANGES
F
). Both of these words will fall
F
) is empty. If the newly