Microcomputer circuits

The heart of the Data Acquisition System is the HP-85 (Hewlett-Packard, 1982) microcomputer which has been interfaced to a Wrenn Counter (Wrenn ert aj., 1975) using a Ludlum model 2200 scaler rate meter (Ludlum Measurements, Inc., 1982), a Rainwise weather station (Rainwise, Inc., 1984), and a water meter. These various components are interfaced to the HP-85 via a peripheral interface circuit as shown in the block diagram of Figure 1. For the interface to function properly, the General Purpose I/O (GPIO) has been configured such that two of its ports (A and B) form a 16-bit input port while ports C and D form a 16-bit output port. 

There are two types of memory used in computers. The main memory is based on integrated circuit chips and all parts can be accessed with great rapidity and with equal ease. In mainframe computers this is known as the main store whilst in smaller computers, including microcomputers, it is called the random access memory (RAM). Some parts of RAM may be reserved for the storage of programs or data which are to be protected from change or accidental erasure. Such a reserved area of memory is called read only memory (ROM). ROM chips, sometimes called firmware, are often used in integrators and microcomputers dedicated to particular tasks. The... 

AT-cut, 9 MHz quartz-crystal oscillators were purchased from Kyushu Dentsu, Co., Tokyo, in which Ag electrodes (0.238 cm2) had been deposited on each side of a quartz-plate (0.640 cm2). A homemade oscillator circuit was designed to drive the quartz at its resonant frequency both in air and water phases. The quartz crystal plates were usually treated with 1,1,1,3,3,3-hexamethyldisilazane to obtain a hydrophobic surface unless otherwise stated [28]. Frequencies of the QCM was followed continuously by a universal frequency counter (Iwatsu, Co., Tokyo, SC 7201 model) attached to a microcomputer system (NEC, PC 8801 model). The following equation has been obtained for the AT-cut shear mode QCM [10] ... 

Nominal 3.6 V batteries have been designed for direct mounting on printed circuit boards for CMOS and NMOS memory support applications. Such cells are normally float charged from the main microcomputer DC power supply and constitute a form of uninterruptible power supply (UPS). 

A silicon chip used in an integrated circuit of a microcomputer has a mass of 5.68 mg. Flow many silicon (Si) atoms are present in this chip ... 

Hardware. The electronics portion of the instrument (Figure 1) consists of a microcomputer configured on three circuit boards a central processing unit... 

In the section on microcomputer components, we discussed the most common basic elements of microcomputers resistors, capacitors, vacuum tubes, transistors, and integrated circuits. All of these components can commonly be found on... 

Microcomputers as we now know them, that is, compact stand-alone computers, came into being in the mid-1970 s with the introduction of microprocessor chips. These combined all of the components of a computer s central processor unit (CPU) on a single integrated circuit chip. 

Fig. 11.17 (a) Scheme of the instrumentation used for in vivo electrochemical experiments, (b) Potentiostatic circuit and microprocessor interface (the electronic components are shown for one of the electrodes only) SDK-85, Intel microcomputer system 7520, D/A converter Ai and As, 741 analogue devices A2 and A4, Burr Brown 3510 As, Burr Brown 3527 VFC-32K, Burr Brown V/F converter 2716, Intel EPROM 8253-5, Intel counter DAC-08, PHI D/A converter R = 1 mfi, 1. (Reproduced from [81] with permission of the American Chemical Society). 

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