|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING HIGH-SPEED microcontrollers from DALLAS SEMICONDUCTOR. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Microcontrollers Many new eight-bit microcontrollers (MK) have appeared on sale. They are very attractive in terms of price-to-performance ratio. However, the cost of development includes not only the price of the MK itself, but also the cost of debugging tools, which are indispensable, and software (if development does not start from scratch). This explains the commitment of domestic developers to x51-compatible MK. Dallas Semiconductor's "High Speed" MCUs are fully software and hardware compatible with the MCS51. However, their possibilities are much wider. They are produced both without program memory and with it. The latter can be one-time (OTP EPROM) or repeatedly programmable, in which case the erasing is carried out by irradiation with ultraviolet rays (UV EPROM). Reprogrammable MKs are of the greatest interest to radio amateurs, therefore, only two members of the family, DS87C520 and DS87C530, are considered in detail in the article. The main technical characteristics of the MK family "High Speed" are given in the table. As you can see, it consists of five modifications that differ in their capabilities. So, in DS80C320 and DS80C323 there is no internal ROM, in DS83C520 there is a mask ROM with a capacity of 16 KB, and in DS87C520 and DS87C530 - a one-time programmable or erasable ROM of the same volume with UV irradiation. External RAM on a chip is available only in the last three modifications, and a clock-calendar is available only in the DS87C530.
PERFORMANCE The increase in the performance of "High Speed" microcontrollers is due to the fact that their machine cycle does not consist of 12 machine cycles, as in 87C51, but only of four. Therefore, at the same clock frequency, the simplest single-cycle instruction is executed by the DS8xC5xx MC three times faster than any x51 representative. So, at the maximum clock frequency of 33 MHz, the execution time of the DS87C520 and DS87C530 is 121 ns, which would be available for the 87C51 only at a frequency of 100 MHz. But not all instructions are executed as quickly - on average, the speed of programs increases by about 2,5 times. This is because some "High Speed" instructions in the MCU take more cycles than the 87C51. PROGRAM AND DATA MEMORY The on-chip program memory occupies the lower addresses in the MCU's address space. Its standard three-level protection against unauthorized access is provided. The external program memory is accessed when the program counter exceeds the maximum value of the internal memory address. Note that this maximum address can be programmatically controlled by setting three bits in the ROMSIZE SFR register - the memory size can be set to 0, 1, 2, 4, 8, or 16 KB. During the execution of the program, you can even completely prohibit work from the internal program memory and switch to work from the external one. On the DS87C520/530 chip are both the standard 256 bytes of RAM, which can be accessed in the same way as the 87C52, and an additional 1 KB of memory. The latter is accessed using the MOVX command. This memory is treated as external, despite the fact that it is physically located on the MK chip. In the address space, it is located from 0000 to 03FF. Accesses to external memory at addresses above 03FF automatically select off-chip memory, if any. Access to the mentioned one-kilobyte RAM array can be programmatically prohibited - in this case, any access to external data memory will be performed in the same way as it is done in the MCS-51 family of microcontrollers. MK DS87C520/530 allow software adjustment of the access time to external memory. The MOVX instruction is executed in a minimum of two machine cycles, moreover, when accessing external memory both on-chip and off-chip. However, to work with "slow" external RAM chips, the number of cycles can increase up to nine. When reset, their number is set to three. DATA POINTERS The standard DPTR, referred to as DPTR0, is located at addresses 82H and 83H, which makes the "High Speed" MCU compatible with the 87C51. The second pointer, located at addresses 84H and 85H, is referred to as DPTR1. Selecting a specific DPTR is done by resetting/setting a zero bit in the SFR register at address 86H. By using two pointers for "from" and "to" addresses, block transfers can be efficiently performed. POWER MANAGEMENT In addition to Idle and Power Down, there is another low power mode called Power Management Mode (PMM). In it, the processor continues its work without any restrictions, however, consumption is reduced by reducing the clock frequency. It is possible to reduce it by 16 or 256 times (modes PMM1 and PMM2, respectively). At a clock frequency of 11059,2 kHz in the standard "High Speed" mode, the MK consume 15,5, in the PMM1 mode - 4,8, PMM2 - 4 mA, (the latter is even less than that of the 87C51 / 52 in the Idle mode, and without stopping processor). In addition, in DS87C520/530 it is permissible to use an internal oscillator operating at a frequency of 2...4 MHz as a clock. However, the indicated frequency is unstable, and therefore this solution cannot be used in devices where accurate measurements of time intervals are required. Decreasing the clock speed proportionally changes the serial link speed. In the "High Speed" MK, technical solutions are implemented that make it easy to eliminate this drawback. To reduce electromagnetic radiation from the MK in cases where the ALE signal is not needed, its generation can be programmatically disabled. SERIAL PORTS AND TIMERS The DS87C520 and DS87C530 have two identical serial ports to the 87C51, with the second using pins P1.2 (RXD1) and P1.3 (TXD1), as well as registers SCON1 (C0H) and SBUF1 (C1H). Both ports can function at the same time, but at the same time operate at different speeds or in different modes. The second port can use only the first timer/counter to set the baud rate. To ensure compatibility, the timers in the considered MKs use the clock frequency divided by 12 as the setting clock. However, you can also switch to the clock frequency divided by 3, which is done by setting the corresponding bit in the SFR register CKCON. The watchdog timer resets the MC whenever it overflows. To avoid these resets, it must be periodically reset, which is only possible in a normally working system. The watchdog timer is incremented once per clock period. By setting the appropriate bits, you can set four values of its recalculation, as a result of which the number of cycles before overflow becomes two to the 17th, 20th, 23rd or 26th power. The timer also sets the interrupt flag (if enabled by software) 512 clocks before reset. UNDER-VOLTAGE RESET, INTERRUPT AND REAL TIME CLOCK Reducing the supply voltage to a value below 4,13 V causes the corresponding internal device of the MK to generate a reset signal, which is held until the voltage returns to the specified level. This does not require any additional external elements or changes in the program. When the voltage drops to 4,38 V, an interrupt signal can be generated (if enabled). MK DS87C520 and DS87C530 have six external interrupts: two standard, similar to those in 87C51, and four additional. The latter differ from the standard ones in that they operate only on the edge or fall of the interrupt signal - for INT2 and INT4, the edge is active, and for INT3 and INT5, the fall. Timer interrupts are handled similarly to the 87C52. Each timer has its own enable flag, vector, and priority. Real Time Clock (RTC), which is equipped with MK DS87C530, allows you to store the current time, date, day of the week, month, year. To do this, it is necessary to connect a quartz resonator with a natural frequency of 32,768 kHz and a lithium battery to the MK in an appropriate way. RTCs have the ability to generate an alarm (ALARM) when the programmed time is reached, while the interrupt flag, if enabled, is set even in micro-consumption mode. Author: A.Gorbachev, Moscow
Machine for thinning flowers in gardens
02.05.2024 Advanced Infrared Microscope
02.05.2024 Air trap for insects
01.05.2024
▪ Image Sensor ON Semiconductor AR0221 ▪ Northerners have bigger brains ▪ Ultra-recycled foods shorten life ▪ Increasing popularity of cell phones with cameras
▪ site section Parameters, analogues, marking of radio components. Article selection ▪ article The graces are on vacation and love is retired. Popular expression ▪ article Can animals cry or laugh? Detailed answer ▪ article Bogorodskaya grass. Legends, cultivation, methods of application
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page