Utilities board

The ECUB, or Utilities board, handles all system housekeeping chores. It connects directly to the ENRB where it attaches to the core logic bus, the environmental sensors, and other test points. It interfaces to the liquid crystal display (LCD), the optional teststation (an ethernet connection), and other external devices. Figure 9-1 “Utilities board” shows the Utilities board functional layout.

The heart of the ECUB is the core logic. This section of hardware connects internally with the EMUC for receiving environmental interrupts and to the EPUC as an interface to the core logic bus. The core logic contains initialization and booting firmware. It also interfaces to the LCD and to serial RS232 links, as well as to ethernet links. An optional teststation can be connected via these links to run diagnostics and configure the system.

The EMUC latches system interrupts, most of which are from environmental sensors located throughout the system. The EMUC and the power-on circuit together control system power-up. The EMUC interfaces to a light-emitting diode (LED) diagnostic display through the power-on circuit.

The EPUC provides the core logic an interface to the core logic bus. There are actually two buses; each one connects up to four EPACs. The EPUC communicates to the EPACs using data packets.

The JTAG (Joint Test Action Group) interface supports a teststation and a mechanism to fan out JTAG to all the boards in the system. It is used only for testing.

The V-Class server uses a test method called scanning to test boards and other hardware units. With the teststation connected to the ethernet between nodes, you can test any part of the system.

The JTAG interface contains a microprocessor to capture packets from the ethernet and apply them to the JTAG test bus controller or to take scan information from the JTAG test bus controller and send it out on the ethernet. The teststation can also read and write every CSR in the system.

Figure 9-1 Utilities board