User guide

8.1.4 Ethernet Address
The Ethernet ID address for the Digital Alpha VME 4 assembly is stored in an
on-board SROM, a 20-pin socketed PLCC. The Ethernet controller’s ENET ROM
register (CSR9) can read the SROM. Each read access initiates 8-bit serial read
cycles from the ENET ROM. Writing to the register resets the pointer of the
ENET ROM to its first location.
Figure 8–3 shows the ENET ROM register.
Figure 8–3 DECchip 21040-AA CSR9 (ENET ROM Register)
31 30 08 07 06 05 04 03 02 01 00
ML013283
DN - Data Not Valid
Ignored
DT - Data
DECchip 21040 CSR9 (48h)
8.2 SCSI Controller
The SCSI controller is based on the NCR 53C810 chip. For full operational
programming details, see the specification for the chip and the NCR 53C720
programming guide.
8.2.1 Connection and Termination
The SCSI bus is routed to the VMEbus P2 connector. The pinning for the
user-defined pins of the connector is provided in Appendix A.
An interface to a standard SCSI cable is handled by the primary breakout
module. This module brings the SCSI bus to a standard 50-pin SCSI connector
pinning for direct connection to an unshielded SCSI A-cable.
Active terminators are controlled by a 6-pin jumper block on the primary
breakout module:
• To enable SCSI termination, jumper pins 1 and 3.
• To disable SCSI termination, jumper pins 3 and 5.
8–6 PCI bus