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Review: PICSTART Development System Microcontrollers with speed: the new PIC series The new PIC-series microcontrollers from Microchip Corpora­tion use new RISC architecture which contain as little as 33 instructions. We review these microcontrollers & the new PICSTART development system. By DARREN YATES Microcontrollers have taken off in the last few years or so, yet the internal structure of most of them is based on the 8-bit microprocessor system that dates back to the days of the Z-80. At the moment, there would hardly be a semiconductor house that doesn’t manufacture at least one micro­ controller. And most have at least a dozen or more in their range. Looking through the databooks, many are simply variations on the same theme with maybe just extra I/O ports. The PIC series from Microchip are radically different from the rest of the pack because of the RISC (reduced instruction set) architecture. There are only 33 instructions in the most basic unit but because each instruction is 12 bits wide, it gives each instruction a much greater degree of flexibility. What’s more, all instructions are single- or two-clock cycle, with most being one clock cycle. This makes time-related programming much simpler than most of the standard 8-bit controllers. The RISC architecture also enables PICs to run very fast. In fact, they can operate at up to 20MHz yet they are still low power devices. At 4MHz, the current consumption is less than 2mA at 5V and only a tiny 15µA at 3V for 32kHz operation, making them This is the initial screen displayed by the MPSTART system. This menu-driven package is used to program most of the PIC series microcontrollers. 36  Silicon Chip ideal for extended battery operation. Further, there are extra features to improve power consumption performance, including sleep modes and low-power clock oscillators. They are also guaranteed to operate down to 2.5V supply. Each device has on-board EPROM memory varying from 512 bytes to 2Kb for program storage, as well as between 25 and 72 8-bit registers for general use. There is also a code protec­tion fuse which can be blown once final code has been programmed in. One of the most useful programming features is the inclusion of an 8-bit real time clock\counter with a programmable prescal­er. This makes it easy to program the device to work as some clock type function. There are two main families of PICs – the PIC16CXX and PIC17CXX series which are tailored for different applications but all with the high-speed RISC system. PIC16C5X series The basic PIC series is the PIC16C54/5/6/7. The PIC16C54 is the simplest and smallest, and comes housed in an 18-pin DIP package, either ceramic or plastic. You can also get it in surface mount. It has 512 bytes of 12-bit EPROM, 32 bytes x 8 bit RAM and 12 I/O lines. The PIC16C55 is the same as the above 16C54 but with 20 I/O lines. It comes in a 28-pin package. The PIC16C56 is also based on the ’54 but with 1Kb of EPROM. The top of the range PIC15C57 has 2Kb of EPROM, 80 bytes of RAM and 20 I/O lines. For most applications, this makes the PIC the ideal single-chip computer since there is no external memory or driver hardware required. In all PICs, the RAM is individu- The PICSTART Development System comes with two manuals: the complete Microchip Databook & the Embedded Controller Handbook. ally addressable when programming whereas the EPROM is addressable in 512-byte pages. The I/O lines are banked in groups of eight so that they can be read as either single inputs or as a byte from say an 8-bit analog to digital converter (ADC). For mass production, the 16CXX series is available in erasable-UV form as well as OTP (one time programmable) for code protection once the device is in the marketplace. Second generation PICs The PIC16C71 is the start of the second generation of PIC micro­controllers which include 14-bit wide instruction sets and only 35 instructions. What sets this apart is the on-board 8-bit ADC. This ADC has four multiplexed analog inputs, sample and hold, 20µs/ channel conversion time and an external reference input. Accuracy is quoted at ±1 LSB. The PIC16C71 also has 1Kb x 14-bit EPROM, 16MHz clock speed, 13 I/O lines (each with individual direction control) and an external interrupt pin. All this is in a package that only has 18 pins. The has been achieved by multiplexing most of the pins to perform two functions. Depending upon the instruction, the pins are set to act as either inputs or out­puts. The I/O pins are capable of sinking and sourcing up to 20mA, which reduces the need for external drivers and helps to reduce the design cost. Power consumption for the ’71 is basically the same as the PIC16CXX series with slightly more current consumed with the ADC in operation. Other 16CXX series features such as power saving sleep mode, 8-bit real time clock/counter, power-on reset and watchdog timer are also included. The watchdog timer is basically a free-running RC oscilla­tor which has a nominal timeout period of 18ms but can be pre­scaled with a division ratio of up to 1:128 to produce a period of 2.5 seconds. Once the timer has timed out, it generates a RESET condition which can be used in programming to either reset the device or branch to another section of code. PIC16C84 All of the devices so far have used an EPROM which is UV-erasable. The 16C84 differs in that it contains a 1Kb x 14-bit electrically erasable PROM for program and a 64 byte EEPROM data memory. This could be used for entering external data which changes from device to device while the program code remains unchanged. It operates down to 2V and has a standby current consump­tion of less than 1µA. The package is an 18-pin outline with 13 I/O lines, capable of 25mA sinking and 20mA sourcing current. Maximum speed is 10MHz with a 400ns instruction cycle. Program interrupts are available from one of four sources – the external INT pin, real time clock overflow, toggling of one of the I/O lines and filling of the data EEPROM. The PIC17CXX series The PIC17C42 represents the latest step in RISC microcon­troller design with 16-bit wide instruction at up to 25MHz clock speed. What makes this device different is that it has four modes of operation: standard micro­­controller mode, secure microcon­troller mode, extended micro­con­troller mode with both internal and external program access, and microprocessor mode with exter­nal program access only. The 17C42 has 2Kb of 16-bit EPROM for internal stored programs or it can address a maximum of 64Kb x 16 memory space outside. In standard microcontroller mode, the 17C42 allows only internal program execution so that only the onboard 2Kb EPROM memory can be April 1994  37 Protect your valuable issues Silicon Chip Binders These beautifully-made binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. ★ High quality ★ Hold up to 14 issues ★ 80mm internal width ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A14.95 (includes postage in Australia). NZ & PNG orders please add $A5 each for postage. Not available elsewhere. Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 979 6503; or ring (02) 979 5644 & quote your credit card number. ➦ Use this handy form Enclosed is my cheque/money order for $________ or please debit my ❏ Bankcard   ❏ Visa   ❏ Mastercard Card No: ______________________________ Card Expiry Date ____/____ Signature ________________________ Name ___________________________ Address__________________________ __________________ P/code_______ 38  Silicon Chip used. Secure mode incorporates code and write protection so that your program code cannot be overwritten or copied. Extended mode allows the inclusion of external memory above 2Kb (between 2Kb and 64Kb) and the use of the internal EPROM below 2Kb. In microprocessor mode, the entire 64Kb memory is mapped externally and the internal EPROM cannot be used. Other features of the 17C42 include two high-speed pulse-width-modulation outputs with 10-bit resolution and 15.6kHz speed. These could easily be used with say an H-pack output drive circuit in part of a switching power supply, for example. There are 232 x 8-bit general SRAM registers and up to 33 I/O lines. As with the other PICs available, it also has a watchdog timer with its own internal RC oscillator as well as three 16-bit timer/counters. For those who require external control, there are 11 external/internal interrupts available as well. One of the more unusual features is the fully featured serial port (USART) which includes a baud rate generator. This can be configured for either full-duplex asynchronous or half-duplex clocked synchronous mode. An 8-bit dedicated baud rate generator which can be programmed is also included. Development system To help the PIC push into the marketplace, Microchip have come up with the PICSTART – a micro­controller development system which mates with any IBM AT. It contains a small PC board which has a connector for your serial port and a zero-force-insertion (ZIF) socket. As part of the system, the software package in­cludes a PIC device programmer called MPSTART; the MPALC Mi­crochip PIC Assembly Language Compiler; and MPSIM, a PIC simula­tor. All software supports the PIC16C54 to 84 devices and can be run on any PC with the following requirements: (1) 1.44Mb drive; (2) hard disc drive; (3) serial port; (4) 640Kb RAM; and (5) DOS 3.3 or higher. A text editor, VGA screen and mouse are highly recommended but not mandatory. The PC board requires a 9VDC 250mA power supply which can quite easily come from a 9VDC plug pack. The board is quite small at just 117 x 76mm and you also get two sample PICs to play with. All programs run under DOS and do not require Windows which is a great idea. The programmer, MP­ START, is activated simply by typing MPSTART<enter>. It’s a menu-driven package which automati­cally sets up the link between the PC board and the computer and warns you when the connection isn’t made, for example, if the power supply is not connected. It has context-sensitive on-line help in case you get into trouble at any stage, as well as normal file handling facilities. The program is completely menu-driven so you don’t have to remember any fancy command calls. MPALC The assembler, MPALC, is a command line driven program which requires your source code to be already in an ASCII format file. To assemble code, you simply add in the source code file­ name and the destination filename of the compiled code plus a number of option directives. For example, the /P option allows you to compile code for a specific device. Thus, “/P 16C54” would compile code specifically for the PIC16C54 controller. MPSIM The MPSIM simulator, which also runs from DOS, allows you to test program files by loading them into the simulator and checking the various registers and ports to check the program’s correctness. Programs can be tested by either single command stepping or execution up to a certain command or address in EPROM. Register values are maintained on-screen at all times. Overall, the PIC-series of micro­ controllers represent a big step forward in microcontroller design. They feature high speed and low cost in terms of both code development time and produc­tion. Watch out for the PICs to make big waves in the micro­con­troller industry. The PICSTART system also includes two manuals: the complete Microchip Databook and the Embedded Controller Handbook. The PICSTART is available from NSD Australia for the bargain price of just $250, which is peanuts compared to many other development systems. You can contact SC them on Sydney (02) 898 0133.