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PART 2. PROCESSOR BOARD 01-P29050H001
14.3 DESCRIPTION
The Processor board provides primary control and
data
manipulations
for the
system
analyzer,
and
con-
tains the following:
•
microprocessor
•
program read only memory (ROM)
•
nonvolatile memory (NVM)
•
random access memory
(RAM)
•
peripheral-interface adapter (PIA)
•
printer
circuitry
•
dual
tone
multifrequency
(DTMF)
encoder/
decoder
•
timing
generator
•
character
generator
Input and
output
information is transferred
through
the PIA and the address, data, and
control
buses.
A block diagram
of
the Processor board is
shown
at
the end
of
this
section
in Figure 14-5,
a schematic
in
Figure 14-6, and
the
printed wiring board
assembly
and
parts list in Figure
14-7.
14.4 THEORY OF OPERATION
14.4.1
MICROPROCESSOR
An
M6809 microprocessor
controls
the
system
ana-
lyzer's
operating
modes.
The device
bas
an 8-bit data
ADDRESS
UNPAGED
0000
B
0800
I
1000
NON
VOLITILE
MEMORY
1800
2000
AOOO
PROGRAM
ROM
FFFF
bus, a 16-bit address
bus,
and
a control
bus which
syn-
chronizes
data transfer
and specialized
processor
functions.
The
microprocessor
uses
a
4-MHz crystal
(Y1)
to provide an
operating
frequency
of
1 MHz on
the
E and
Q
lines.
14.4.2
MEMORY
14.4.2.1
Memory
Access
To allow the
microprocessor's
16-bit address
bus
to
access
more than 64K
of
memory, the memory is
structured
in
pages,
as shown
in Figure
14-2
The pages
are
broken down
into chip-select
blocks.
To
select
a
page of
memory,
the
processor uses 4
outputs
(PBO,
PB1, PB2, and PB3) from PIA
U38. (See section
13,
All
for a description of PIAs.) These
signals
work
in
conjunction
with the address decoders
(U7
and US) to
select the proper memory device.
14.4.2.2
Program Read
Only
Memory
(ROM)
The Processor Board's program memory is located
in
the
unpaged area
of
the memory map, page
2
and
page 4. The ROM
consists
of three 32K
X
8-bit read-
only memory
devices.
The program memory for the
options
is
on the pages
shown
in Figure 14-2.
PAGE
1
PAGE 2
PAGE 4
~pRAM
I
PROGRAM
PROGRAM
EPROM
EPROM
7tl42·
1
Figure
14-2.
M
emory
Map
14-3
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