A Date with KIM, May 1976, BYTE Magazine
Contents
1. use it to drive a small speaker for micro processor music programmed in a manner similar to the Kluge Harp of October BYTE page 14 Each line can be separately pro grammed for input or output by writing a status word into the correct memory location The cassette interface is carefully thought out and should be foolproof Half of the executive ROM is devoted to the cassette interface software which includes rudimen tary file management and sophisticated pro grammed equivalents to UART operation This software allows multiple dumps to a single cassette A header written on each output segment allows you to say in effect find me program number 34 on the tape and load it starting at location A check sum is stored at the end of each segment and the user is immediately informed if the computed checksum doesn t match when the tape is read back in You can even record voice data between segments of digital data the interface will ignore the voice This feature could be used to verbally record the instructions for a game and then auto matically load and run it Both high and low level outputs are provided to interface with any type of cassette recorder It s not a vital feature but it indicates the care with which the entire system has been thought out The TTY interface is for a standard 20 mA current loop figure 1 shows how modified it for an RS 232 interface A unique feature of the software is2. Hardware Manual A so shown in this picture is the KIM monitor listing copy which must be requested separately and is a must if you are to take advantage of KIM s sub routines in applications programs A Date with KIM KIM 1 printed circuit board and attach a 5 volt ampere power supply to the 44 pin edge connector provided You ll also need a supply of 12 V for the cassette interface but a handful of flashlight bat teries should work fine since only about 50 mA of 12 V is required and that only when the interface is being used The name KIM is an acronym for Key board Input Monitor The name really des cribes the ROM executive routines not the whole unit but it s a pleasant change from the manufacturer s name followed by a number It s also significant that the system derives its name from its software The KIM 1 board can be operated in one of two modes using the on board keypad and LED display or using a serial terminal The keypad and hexadecimal display is infinitely easier and less error prone than throwing toggle switches and reading results from binary lamps In fact for program entry and many simple applications prefer the 23 key keypad and bright LED display to my slow noisy Teletype The keys have a good positive feel to them MOS Tech Photo 2 The KIM 1 proc essor as it is removed from its box The MOS Technology product comes in a neat package which has one foam pad ded and s
3. machine cycle of multicycle instructions while not essential is very instructive Special sections of the manual are devoted to interrupt handling and use of the stack pointer This is vital information often glossed over in other manuals have to admit that have not yet digested all the information in the 150 page hardware manual which came with my KIM since my main interest is in programming my system as soon as possible However the manual seems to have a solid emphasis on IO interfacing and usage of the control lines The third manual provided is the actual KIM user s manual This 100 page document explains how the keypad cassette interface and terminal interface are to be used It gives 12 a few basic programming examples includ ing an example which goes through the entire design of a simple application using the IO lines My only complaint is that no sample program was provided for the use of the programmable timer or the ROM execu tive subroutines Also the listing of KIM should have been supplied as a standard item Also included in the package is a pocket reference card for the instruction set and a wall size schematic of the entire KIM board Two other useful documents are available from MOS Technology on request One is the manual for the 6500 cross assembler which is available on several commercial time sharing systems The other is the well commented listing of the executive programs stored in ROM as m
4. Richard S Simpson 314 Second Av Haddon Heights NJ 08035 MICROCOMPUTERS MICROCOMPUTERS MICROCOMPUTERS Here it is In the November 1975 BYTE Dan Fylstra reviewed the capabilities of the MOS Technology 6501 microprocessor chip in an article titled Son of Motorola page 56 The article stated that it will be three to six months before you see a 6501 designed into a kit Well MOS Tech nology has gone one better and introduced not a kit but a completely assembled tested and warranteed microcomputer with a price tag of only 250 Using the 6502 processor chip a 6501 with an on chip clock the microcomputer features 1 K of RAM 2 K of ROM containing the system executive a complete audio cassette interface a serial terminal interface 15 bidirectional IO lines a 23 key keypad and a six digit LED display This completely assembled one board com puter has all the programming features of the 6502 at a very competitive price If you have been hesitating over buying a microcomputer because of the difficulty of assembly and the fear that it won t work when you re finished KIM 1 is for you The only assembly required is to attach six self adhesive plastic feet to the back of the Photo 1 When you first open your KIM 1 box you see a thick layer of docu mentation including a large wall chart of the system s hardware details an MCS650X Instruction Set Summary card K M 1 User Manual Programming Manual and
5. accumulator in hex on the terminal requires a simple one instruction subroutine call Those readers who have had to invent their own terminal interface soft ware will have a deep appreciation for this capability Similar subroutines are provided for reading characters from the terminal or keypad printing one or a string of ASCII characters or writing digits in the LED display To round out the terminal interface software is provided in ROM to read and punch paper tape if your terminal is so equipped Again care has been taken to provide checksums on the punched tape which is automatically verified when the data is reloaded This kind of attention to detail reflects the high caliber of the MOS Technology offering One reason for this is the fact that MOS Technology sells a size able portion of the KIM units to industrial users This policy of building to industrial rather than consumer standards is also evident in the quality of the PC board the 10 PC artwork and the fact that the board is coated with a solder mask a plastic coating which protects the printed wiring To further emphasize their faith in KIM MOS Technology gives you a 90 day warranty on the entire KIM system not just the com ponents Mail in repair service is available even after the warranty expires Interval Timer Another feature of KIM which is finding its way into more and more microprocessors is the inclusion of a program controlled interval timer T
6. automatic data rate detection As soon as the system is powered up the user types a RUBOUT character on his terminal The software 9 If you have been hesitating over buying a micro computer because of the difficulty of assembly and the fear that it won t work when you re finished then KIM 1 is for you KIM 1 derives its name from the software a sig nificant indication of the importance of good user support programs 20mA CURRENT LOOP TO KIM I RS 232 RS 232 CONVERSION APPLICATION CONNECTOR CONNECTOR Figure 1 One way to in terface KIM 1 with an RS 232 compatible ter minal is illustrated in this diagram Opto isolators are used to accomplish the coupling The RS 232 pins 1 2 and 3 will be suffici ent for terminals which do not involve handshaking on some terminals pins 5 6 8 and 20 of the stand ard RS 232 plug may have to be tied together to bypass handshaking sig nals 4 N33 calculates the data rate anything from 110 to 1200 baud is acceptable and auto matically adjusts all further conversation to that rate No additional timing standards or switches are required for the interface The real beauty of the terminal interface is in the software not the hardware On request MOS Technology supplies a com plete listing of KIM All the executive ROM software subroutines are documented and available to the user referencing this well commented listing Thus to print the con tents of the
7. entioned carlier In summary the KIM is an excellent microcomputer requiring no assembly and which is very attractively priced The only auxiliary equipment required is a power supply and a cassette recorder The manuals are among the best available and the built in keypad and display make KIM easy to get started with The terminal interface and ease of memory expansion make it easy to upgrade as your requirements increase Make a date with KIM you ll enjoy it
8. he KIM board actually contains two programmable timers but one is dedicated to control the keypad and cassette interface Any count from 1 to 256 can be loaded into the timer by writing to the timer s memory location The user can control the scale of the timer by pro gramming it to count every clock pulse or to count every 8th 64th or 256th clock pulse This prescaling of the counter is done by decoding the last two address bits for the timer Thus the time scale is controlled by which memory location is loaded with the count You might consider using a similar scheme whenever you have to write more than eight bits to control an external device Just use the least significant address bits as data When the timer has counted down to zero a software interrupt is generated noti fying the program that time has run out As soon as the interrupt is issued the timer continues to count past zero into negative numbers at the clock rate If the program is servicing other interrupts it can read the counter register to determine how long ago in machine cycles the timer interrupt occurred Memory Expansion If you are interested in expanding the KIM memory beyond the 1K provided you ll be glad to know that all the decoding for the first 4 K is provided right on the KIM board All you need to provide is 4 K more of RAM chips and some buffers There are two connectors on the KIM board one called the expansion connector is fo
9. r adding memory and bus oriented devices The second connector called the application connector interfaces directly to the outside world The expansion connector has all the address data and memory control signals The application connector terminates the lines for the audio cassette the terminal send and receive signals and the 15 IO lines Connections are also provided so that the keypad can be removed from the KIM board and mounted elsewhere a useful feature if Photo 3 Wiring for Stand Alone Use With due re spect to the instructions in the KIM 1 user s manual and addition of some mis cellaneous parts the re sults will be a wiring har ness similar to that shown here Wires have been attached and labelled for GND 5 volts and 12 V The audio cassette inter face has been brought out to an RCA style phono jack assembly purchased at a retail electronics store along with interconnection cables for the recorder in put and output This setup enables the user to enter and test out programs through the KIM 1 control panel and LED display you want to wrap up the KIM printed circuit board in sheet metal along with a power supply Documentation The documentation which comes with KIM is thorough and comprehensive Any regular reader of BYTE should have no trouble following the details of the 200 page programming manual There are plenty of examples and the explanation of the opera tions which occur in each
10. tatic protected KIM 1 board as its bottom layer nology should know about such things since they are a major manufacturer of chips for calculators The switch in the upper right corner of the keypad puts the machine in single instruction not single cycle mode When the switch is on each depression of the GO button causes a single instruction of your program to be executed Control is then returned to the executive program in ROM and the contents of all six machine registers PC X Y S P and the accumula tor are stored in fixed memory locations where you can easily examine them through the keypad or terminal and then GO to the next instruction This is an important capability since if you just halt a micro processor after each instruction there is no way of examining the registers they re all inside the chip won t go into any detail on the instruc tion set see Dan Fylstra s article for that except to say that it is comprehensive The variety of addressing modes makes complex programming especially when processing lists a lot easier The 6502 architecture has no IO register or IO instructions so any memory location can become an IO port if you build the hardware for it KIM comes with a built in 15 line bidirectional 1O interface TTL levels are acceptable of course and one of the lines can supply enough current 5 mA to directly drive a power transistor The manual shows how to
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