FullFlex
Document #: 38-06082 Rev. *G Page 10 of 51
edge. All transactions on the address, control, data input,
output, and byte enables will occur on the C rising edge.
Selectable Pipelined/Flow-through Mode
To meet data rate and throughput requirements, the FullFlex
families offer selectable pipelined or flow-through mode. Echo
clocks are not supported in flow-through mode and the DLL
must be disabled.
Flow-through mode is selected by the FTSEL pin. Strapping
this pin HIGH selects pipelined mode. Strapping this pin LOW
selects flow-through mode.
DLL
The FullFlex familes of devices have an on-chip DLL. Enabling
the DLL reduces the clock to data valid (tCD) time allowing
more set-up time for the receiving device. For operation below
100 MHz, the DLL must be disabled. This is selectable by
strapping LowSPD low.
Whenever the operating frequency is altered beyond the Clock
Input Cycle to Cycle Jitter spec, the DLL is required to be reset
followed by 1024 clocks before any valid operation.
LowSPD pins can be used to reset the DLL(s) for a single port
independent of all other circuitry. MRST can be used to reset
all DLLs on the chip, for information on DLL lock and reset
time, please see the Master Reset section below.
Echo Clocking
As the speed of data increases, on-board delays caused by
parasitics make providing accurate clock trees extremely
difficult. To counter this problem, the FullFlex families incor-
porate Echo Clocks. Echo Clocks are enabled on a per port
basis. The dual-port receives input clocks that are used to
clock in the address and control signals for a read operation.
The dual-port retransmits the input clocks relative to the data
output. The buffered clocks are provided on the CQ1/CQ1 and
CQ0/CQ0 outputs. Each port has a pair of Echo clocks. Each
clock is associated with half the data bits. The output clock will
match the corresponding ports I/O configuration.
To enable Echo clock outputs, tie CQEN HIGH. To disable
Echo clock outputs, tie CQEN LOW.
Deterministic Access Control
Deterministic Access Control is provided for ease of design.
The circuitry detects when both ports are accessing the same
location and provides an external BUSY flag to the port on
which data may be corrupted. The collision detection logic
saves the address in conflict (Busy Address) to a readable
register. In the case of multiple collisions, the first Busy
address will be written to the Busy Address register.
If both ports are accessing the same location at the same time
and only one port is doing a write, if tCCS is met, then the data
being written to and read from the address is valid data. For
example, if the right port is reading and the left port is writing
and the left ports clock meets tCCS, then the data being read
from the address by the right port will be the old data. In the
same case, if the right ports clock meets tCCS, then the data
being read out of the address from the right port will be the new
data. In the above case, if tCCS is violated by the either ports
clock with respect to the other port and the right port gets the
external BUSY flag, the data from the right port is corrupted.
Table 4 shows the tCCS timing that must be met to guarantee
the data.
Table 5 shows that, in the case of the left port writing and the
right port reading, when an external BUSY flag is asserted on
the right port, the data read out of the device will not be
guaranteed.
The value in the busy address register can be read back to the
address lines. The required input control signals for this
function are shown in Table 8. The value in the busy address
register will be read out to the address lines tCA after the same
amount of latency as a data read operation. After an initial
address match, the BUSY flag is asserted and the address
under contention is saved in the busy address register. All
following address matches cause the BUSY flag to be
generated, however, none of the addresses are saved into the
busy address register. Once a busy readback is performed,
the address of the first match that happens at least two clocks
cycles after the busy readback is saved into the busy address
register.
Table 3. Data Pin Assignment
BE Pin Name Data Pin Name
BE[7] DQ[71:63]
BE[6] DQ[62:54]
BE[5] DQ[53:45]
BE[4] DQ[44:36]
BE[3] DQ[35:27]
BE[2] DQ[26:18]
BE[1] DQ[17:9]
BE[0] DQ[8:0]
Figure 2. SDR Echo Clock Delay
Input Clock
Echo Clock
Data Out
Echo Clock
Table 4. tCCS Timing for All Operating Modes
Port A—Early Arriving Port Port B—Late Arriving Port tCCS
C Rise to Opposite C Rise Set-up Time for Non-corrupt Data UnitMode Active Edge Mode Active Edge
SDR C SDR C tCYC(min) – 0.5 ns