Specifications

Theory of Operation
4 4
4-15
SRFIFO(FSIG) and does the above action). The only apparent purpose of these writes
is testability.
EXM Expansion Interface
The EXM expansion interface is electrically similar to the PC/AT ISA (16-bit data)
bus. In addition, it contains a signal EXMID* used for dynamic recognition and
configuration of EXMs. EXMs respond to one or more I/O addresses in the range
100h - 105h only when their EXMID* line is asserted. EXMs are required to return a
unique EXM ID byte in response to a read from I/O address 100h.
This ID byte is the same identification byte discussed earlier in Chapter 3, BIOS
Configuration in the section on the EXM Menu.
The EXM expansion interface is provided on rows A, C, and D of the EPC-8's 4-row
DIN P2 connector. The subplane carries the EXM interface to other modules, such as
to EXM modules and the EXP-MX Mass Storage module. These EXM interface
signals are not passed through to the VMEbus.
Further information on the EXM expansion interface, its connectors, and standards for
building EXMs is available upon request.
VME Interface
Connectivity
The EPC-8 module connects to the VMEbus J1 connector directly and uses all of the
defined VMEbus lines except SERCLK, and SERDAT. Connection to the J2 con-
nector is through the subplane's 4-row DIN connector B row. Connections to the VME
J2 backplane are on the B row and are power and ground, address lines A31-A24,
data lines D16-D31.
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)
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