CHAPTER 7
THEORY OF OPERATION
75
CHAPTER 7. THEORY OF OPERATION
7.1. Introduction
This section describes the operation theory of this IEEE-488 interface card. A
thorough understanding of the theory will increase its usefulness and help avoid future
problems.
7.2. Block Diagram Description
Figure 7-1 is the block diagram of this interface card. This interface transfers data in a
bidirectional fashion between the PC-Bus and the IEEE-488 instrument bus. The
IEEE-488 bus driver is stored in the on-board ROM. When the application program
calls the IEEE-488 procedures, the procedures call the driver routines in the ROM and
generates the necessary bus command sequence and then transparently passes the data
string to or from the bus device.
All of the major elements of this card are interconnected by the data bus of the PC-
Bus.
When an IEEE-488 bus driver is called, the CPU starts the routine stored in the ROM.
The driver routine controls the IEEE-488 INTERFACE CONTROLLER to execute
the necessary command sequence.
The on-board RAM is for the storage of the interface parameters, such as the IEEE-
488 address of the controller. The IEEE-488 INTERFACE CONTROLLER is an IC
chip which provides an interface between a microprocessor system and the IEEE-488
standard bus. This IC is controlled and configured through 8-bit I/O mapped registers
and enables all aspects of the standard to be implemented, li including talker, listener
and controlJer functions.
The clock/calendar chip and the battery provide a 24-hour clock and calendar for the
system.
Содержание PCLS-848-P
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