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6. Hardware Structure and
System Signals
In this chapter, the hardware components of the
MCDS are described and the names and functions of
the system signals are discussed.
Module Descriptions
The modules included in the MCDS System are
described below. The block diagram in Fig. 11 shows
the major functions of the CDP18S601 and the
CDP18S652 and how they are interconnected.
The CDP18S601
Microboard
Com putercontainsa
CDP1802 CPU, a crystal-controller clock, read-write
memory, parallel I/O ports, a serial communications
interface, power on reset, and an expansion interface.
Four on-board sockets are provided for read-only
memory, enabling the user to select 4 to 8 kilobytes of
mask-programmable ROM or PROM, depending on
the applications.
The
central processor
for the CDP18S601 is the 8-
bit silicon-gate CMOS RCA COSMAC Micro
processor CDP1802. The CDP1802 has 16 general-
purpose registers each 16 bits wide. Any one of these
registers may be dynamically designated as the
program counter, thereby giving the system multiple
program states. Each register may also be used for data
storage or as memory pointers for subroutines, I/O
stacks, and the like. One register each is designated for
DMA and Interrupt pointers. The CDP1802 provides
a serial data out connection, Q, and four external flag
input pins, EF1 through EF4, which may be used as
test and branch conditions independently.
Eight MWS5114 RAM’s supply the Development
System with 4 kilobytes of CMOS
read-write memory.
Four sockets are provided for four or eight kilobytes of
nonvolatile
read-only memory.
RCA CDP1834 mask-
programmed CMOS ROM’s or 2708, 2758, or 2716
2 0 PROGRAMMABLE
1 /0 LIN E S ( P 2 )
R S 2 3 2 C (J 2 ) OR
2 0 - m A L 0 0 P (J I)
4 / 8
4
KILOBYTE
KILOBYTE
ROM
RAM
4
M W S5II4
SOCKETS
( 8 )
JL
CONTROL BUS
xz
C D P I8 S 6 5 2
R E S E T /
RUN
LOGIC
ADDRESS
LATCH AND
DECODE
1 0 2 4 -
BYTE
RAM
JsZ-
U T6 2
BASIC 3
ASSEM
B L E R /
EDITOR
P P
DATA BUS
ADDRESS BUS
MICROBOARD BUS INTERFACE PI
9 2 C L - 3 4203
Fig. 11—B lock diagram o fR C A COSMAC M icroboard Com puter Development System CDP18S694.
