M1AFS600-PQ208 Datasheet, PDF (169/334 Pages) Microsemi Corporation – Fusion Family of Mixed Signal FPGAs

Fusion Family of Mixed Signal FPGAs
At the system level, the skew circuit can be used in applications where transmission activities on
bidirectional data lines need to be coordinated. This circuit, when selected, provides a timing margin that
can prevent bus contention and subsequent data loss or transmitter overstress due to transmitter-to-
transmitter current shorts. Figure 2-110 presents an example of the skew circuit implementation in a
bidirectional communication system. Figure 2-111 shows how bus contention is created, and Figure 2-
112 on page 2-154 shows how it can be avoided with the skew circuit.
Transmitter 1: Fusion I/O
Transmitter
ENABLE/
DISABLE
Skew or
Bypass
Skew
Routing
EN(r1) _{Delay (t1)}
ENABLE(t1)
EN(b1)
Bidirectional Data Bus
Transmitter 2: Generic I/O
EN(b2)
Routing
Delay (t2)
ENABLE(t2)
Figure 2-110 • Example of Implementation of Skew Circuits in Bidirectional Transmission Systems Using
Fusion Devices
EN (b1)
EN (b2)
ENABLE (r1)
ENABLE (t1)
Transmitter 1: OFF
Transmitter 1: ON
Transmitter 1: OFF
ENABLE (t2)
Transmitter 2: ON
Transmitter 2: OFF
Bus
Contention
Figure 2-111 • Timing Diagram (bypasses skew circuit)
Revision 4
2- 153