Datasheet

SCEA022
7–262
Achieving Maximum Speed on Parallel Buses With Gunning Transceiver Logic (GTLP)
3 Transfer Modes
For a synchronous system, as the name suggests, it is important for the transferred data to refer
to a common system-clock signal. Every participant in the system then gets the active edge of
system clock as a reference and a data signal, which refers to the system clock.
In this section, two synchronous transfer modes are described:
• Central-synchronous system clock (CSSC) mode
• Source-synchronous system clock (SSSC) mode
System parameters that have an important role in affecting the maximum clock speed, in
conjunction with the calculation of the time budget, are discussed in the following subsections.
3.1 Parameters for the Time Budget
Parameters for the time budget are assigned to different sources (see Figure 5). The transmitter
and clock-distribution devices have skew values and additional propagation time as a result of
simultaneous switching. Flight time represents the propagation delay time of the signal via the
bus. Finally, the setup and hold times of the receiver must be taken into account.
Skew
Simultaneous Switching Delay
Setup Time
Hold Time
Flight Time
Figure 5. Important Parameters for the Time Budget