APPLICATION BRIEF
AB-8
October 1981
© INTEL CORPORATION, 1981
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INTEL.:S E2 PROMS CAN BENEFIT BOTH THE MANUFACTURER AND THE USER The Industrial setting is finding Programmable Controllers and Data Loggers to be growing in sales as the cost of electronic hardware decreases, and as processes become more complex. All too often, the Industrial Process is restrained, not by its speed and dependency limitations, but by that of its supporting devices. As the cost of electronics hardware goes down, the cost of process downtime is going up because of the increased cost of labor, materials and opportunity. This brief discusses the typical system architecture of Programmable Controllers and Data Loggers, then examines the current use of battery-backed RAM in the systems, and notes benefits received from using Intel E 2 PROMs as an alternative to the battery-backed RAM. Typical system architecture centers around a 16-bit microprocessor with a keyboard, display, tape drive, 110 and memory. Since the system operation consists of sequentially scanning the inputs, processor operation consists of retrieving an instruction from the user memory, executing it via the operating program, using the scratchpad, performing any output required, and repeating the cycle. Should the user program need to be loaded into user memory, it can be done by keyboard, tape load or a remote processor. See figures 1 & 2.
does not want the inconvenience of reloading it (by tape or keyboard) every time the power is interrupted. Should the process be of a batch nature, the microprocessor scratchpad and data table also need nonvolatility so that if the process is interrupted by a power failure, it can be started again without initializing the process. In Data Loggers, the clock is battery backed up in order to provide correct program function on startup per time of day. The RAM and battery back-up of the user program does serve its purpose but is susceptible to the rigors of the harsh industrial environment. Occasionally problems are caused for the user when the batteries or power sense circuitry fail to do their work. The inherent problem of batteries is that their lifetime of 1 to 4 years (depending on use) is not as long as the IO-year-plus life of the machine whose memory they back up. They must therefore be checked and replaced during the lifetime of the machine thus incurring high costs and paperwork for the user. The major concerns of industry users are twofold. First is that the batteries sometimes fail during a shut down. Second is that the power sensing circuitry can be affected by transients. Both of these can cause loss of the user program which hurts the user as it causes costly process downtime. The user does not blame all the problems of user memory loss on the reliability of the batteries and sensing circuitry. Often it is an operator who carelessly allows condensation, fluids or temperature extremes to be exposed to the
The battery-backed up RAM is used to store the userspecified program. It must be non-volatile as the user
IKEYBOARD~
I I
DISPLAY
TAPE
~
MICROPROCESSOR
Y
) -
I/O
OPERATING PROGRAM
MICROPROCESSOR
EPROM
ORPRQM
PROM OR EPROM
SCRATCH PAD
USER PROGRAM SCRATCH PAD
RAM
USER
PROGRAM
e2 PROM RAM
Figure 1. Programmable Control System Architecture
Figure 2. Data Logger System Architecture
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Controller or Logger. All these factors can cause user memory loss through short circuits or through battery failure due to sensitivity to temperatures other than at room.
-No loss of user program due to power transients or operator negligence. Costly downtime can be avoided. -Possible elimination of tape as a secondary storage medium saving an initial investment of hundreds of dollars.
The costs of process downtime to the user can be from hundreds to thousands of dollars per hour. The user accepts that power failures are beyond his control but process downtime after a failure is controllable. If a user has to reload the program due to battery failure. insufficient charging, or sensing circuitry failure, the actual loading can take 10 minutes to many hours. This depends on how many machines are being used and and whether the user has already had experience (and downtime) and therefore knows the immediate solution from a previous repair. The Intel E 2 PROMs offer the solution to drawbacks of battery-backed up user memory as they are truly non-volatile and offer the fast read access speed required by the microprocessor.
-Elimination of battery costs and servicing costs for user program retention. This can be in the order of $10 or more each year depending on battery type, service method, and shut downs per year. -Increased confidence in machine reliability. The benefits to the manufacturer lie in the fact that over the life of the machine, costly customer production downtime will be avoided and therefore the customer will have a higher level of confidence in the machine's memory retention. This translates directl~ into a higher sales price for the manufacturer. Intel's E PROMs are a value adder to the manufacturer's products. They enhance product features, increase product value, reduce customer maintenance, reduce manufacturer's warranty costs and offer true non-volatile memory.
The benefits to the user are as follows: -No battery failure during a shutdown necessitating a reload upon startup and production loss. Production savings using E2 can be up to many thousands of dollars.
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