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2-25
Architecture
LatticeECP/EC Family Data Sheet
Figure 2-29. Output Register Block
Figure 2-30. ODDRXB Primitive
Tristate Register Block
The tristate register block provides the ability to register tri-state control signals from the core of the device before
they are passed to the sysI/O buffers. The block contains a register for SDR operation and an additional latch for
DDR operation.
Figure 2-31 shows the diagram of the Tristate Register Block.
In SDR mode, ONEG1 feeds one of the flip-flops that then feeds the output. The flip-flop can be configured a D-
type or latch. In DDR mode, ONEG1 is fed into one register on the positive edge of the clock and OPOS1 is
latched. A multiplexer running off the same clock selects the correct register for feeding to the output (D0).
D
Q
D
Q
D-Type
ONEG0
From
Routing
CLK1
Programmed
Control
DO
Latch
LE*
*Latch is transparent when input is low.
OPOS0
OUTDDN
/LATCH
0
1
0
1
To sysIO
Buffer
ODDRXB
LSR
Q
DB
CLK
DA