RadiSys EPC-5A, Hardware & Software Reference Manual

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6 6
6. The VMEbus Interface
This chapter describes the EPC-5A VMEbus interface as seen by a program. Users
should avoid direct use of most of these facilities. Whenever possible, the VMEbus
interface should be accessed through the EPConnect software, an easy-to-use,
high-level interface that frees you from most machine-dependent considerations.
Connectivity
The EPC-5A module connects to the VMEbus J1 connector directly and uses all of the
defined VMEbus lines except
SERCLK , SERDAT , and +5V STDBY . Connection
to the J2 connector is through the subplane’s 4-row DIN connector B row. The only
connections to the VME J2 backplane on the B row are power and ground, address
lines
A31-A24 , and data lines D16-D31 . Pin 30, Row A, the VXI-defined module
identification (
MODID
) line is also connected. Pin A30 is an input driving one gate
input and an 825-ohm pull-down resistor. It may be disabled by removing the
MODID jumper on the EPC-5A. If necessary, see Chapter 2, Configuring the
EPC-5A.
VMEbus System (Slot-1) Controller Functions
Every VMEbus system must have a System (Slot-1) Controller. The Slot-1 controller
provides the following functionality:
•
Serves as the bus arbiter (priority or round-robin)
•
Drives the 16 MHz SYSCLK signal
•
Starts the IACK daisy chain
•
Provides Bus Timer function