IMS 5000 Series Manual page 36

HARDWARE SUMMARY
TTL RS-232 RS-232
INTERFACE INTERFACE INTERFACE
PARALLEL UART 1 UART 0
PROGRAM
PORT INTERVAL
1
1
TIMER
ERRUPTS
1
NTROL BUS
TA BUS
DRESS BUS
ROM
MEMORY
INT
AD
S-100
BUS DA
CO
Figure 2-12
Model ...... Board Block Diagram
2048 x 8 EPROM
The 2716 EP ROM contains the IMS Initial Program Loader OPL). Its address
space is shunt selectable.
J
Programmable Interval Timer (8253)
The 8253 functions as a general-purpose, multi-mode timing element that can be
considered as an array of I/O ports.
The 8253 allows the programmer to set up tlmtng loops in the system software
to generate accurate time delays under software control. The user may initialize
one of three counters with the desired quantity and, upon command, count out
the delay and interrupt the CPU when it has completed its tasks. This minimizes
software overhead and allows multiple delays that can be easily maintained by
assignment of priority levels.
IMS International
5000 Series Microcomputer s/7.0 1.8 3/pag e 34