ABSTRACT
ASCB-D is a TDMA-based protocol where a minor frame (the fastest period) is running at 80 Hz. Figure 13.2 depicts the bus traffic of one bus. First, master NICs send synchronization pulses (sync pulse) followed by periodic traffic (Ethernet frames). The beginning of each frame is called a frame tick. The physical layer of the buses is based on 10Mbit/s Ethernet using twinax cables and connectors. Figure 13.2 shows the minimum period (called minor frame) on the bus. Two sync pulses (special Ethernet frames with synchronization information) are the first frames on the bus. The two time servers that are connected to this bus send these sync pulses. After this, individual NICs (i.e., both the time servers as well as the time slaves) send based relative to frame tick according to a predefined dispatch schedule, where the frame tick is the beginning of a minor frame. The synchronized time of NICs is used for avoidance of collisions on the network. ASCB is part of the Primus Epic architecture, which does not leverage sub-frame timing (i.e., on actions based on time offsets within the minor period). Chapter 14.2 will explain details.
