Minimal system design based on S3C4510B microprocessor

Introduce the S3C4510B ARM microprocessor and the smallest system based on the processor, and outline the selection of the system’s peripheral application circuits for users to design and develop themselves.

Introduction: Introduce the S3C4510B ARM microprocessor and the smallest system based on the processor, and outline the selection of the system’s peripheral application circuits for users to design and develop themselves.

ARM (Advanced RISC Machines), it can be considered as the name of a company, it can also be considered as a general name for a type of microprocessor, or it can be considered as a technical name, habitually called “Advanced Reduced Instruction Set” Computer Machine Company”. At present, the number of device applications of various ARM microprocessors has far exceeded that of general-purpose computers. In the industry and service fields, digital machine tools, smart tools, industrial robots, and service robots using ARM microprocessors are gradually changing the traditional industrial production and service methods. Therefore, the development and application based on ARM microprocessor is becoming the trend of application technology in the data age. This article introduces the construction of the smallest system of S3C4510B ARM microprocessor, and gives the selection of related peripheral devices of the system.

2 S3C4510B

S3C4510B is a cost-effective 16/32-bit RISC microprocessor based on the Ethernet application system of South Korea’s Samsung company (Samsung). It contains a low-power, high-performance 16/32-bit ARM7TDMI RISC processor core designed by ARM. , It is most suitable for applications that are sensitive to price and power consumption.

S3C4510B has a working voltage of 3.3V, a total high frequency of 50MHz, and a 208-pin QFP package. Its external data bus (bidirectional, 32-bit) supports external 8, 16-bit, 32-bit data width; 22-bit address bus can address every ROM/SRAM group, FLASH memory group, DRAM group and external I/O group Address range of 4M words (16M bytes). The microprocessor has built-in 37 32-bit registers (31 general-purpose registers and 6 status registers). At a certain moment, whether the registers can be accessed is determined by the current working state and operating mode of the processor. The on-chip peripheral function modules of a single S3C4510B include an external bus controller with bus request/response pins; a 32-bit system bus arbiter; an integrated command/data Cache (8KB) ​​that can be configured as internal SRAM ); 1 IIC interface that only supports master mode; 1 Ethernet controller; 2 HDLC (high-level data link control) channels with buffer descriptors; 1 DMA controller; 2 can work in DMA mode or UART module in interrupt mode; 2 programmable 32-bit timers; 18 programmable I/O ports; 1 interrupt controller with 21 interrupt sources and 1 PLL circuit.

3 hardware design

3.1 Minimal system design

The minimum system is composed of the basic circuits necessary to ensure the reliable operation of the microprocessor. The minimum system of S3C4510B is composed of S3C4510B, power supply circuit, crystal oscillator circuit, reset circuit and JTAG interface circuit. Their connection relationship is shown in Figure 1.

Minimal system design based on S3C4510B microprocessor

3.1.1 Power supply circuit

In the system, S3C4510B and some peripheral devices require 3.3V power supply, and some devices require 5V power supply. In order to simplify the design of the system power supply circuit, the input voltage of the entire system is required to be a 5V DC regulated power supply. In order to obtain a reliable 3.3V voltage, the LT1085CT-3.3 DC-DC converter produced by Linear Technology is selected here. Its input voltage is 5V, the output voltage is 3.3V, and the output current can reach 3A. The power circuit is shown as in Fig. 2.

3.1.2 Crystal oscillator circuit

This circuit is used to provide working clock to S3C4510B and other circuits. In view of the fact that active crystal oscillators are superior to passive crystal oscillators in working reliability and accuracy, an active crystal oscillator is used in the system. According to the highest operating frequency of S3C4510B and the operating mode of the PLL circuit, a 10MHz active crystal oscillator is selected. After the frequency is multiplied by the internal PLL circuit of the S3C4510B, the frequency can reach up to 50MHz. The internal PLL circuit combines the functions of frequency amplification and signal purification. Therefore, the system can obtain a higher operating frequency with a lower external clock signal. The crystal oscillator circuit is shown as in Fig. 3.

3.1.3 Reset circuit

This circuit mainly completes the power-on reset of the system and the user’s button reset function when the system is running, which is helpful for the user to debug the program. The IMP708TCSA type reset circuit produced by IMP is used here. Its working voltage is 3.3V. It has 1 manual reset input pin and 2 reset output pins (the high-level active pin and the low-level active pin are each 1), which can meet the requirements of different reset signals. The reset circuit is shown as in Fig. 4.

Minimal system design based on S3C4510B microprocessor

3.1.4 JTAG interface circuit

JTAG (Joint Test Action Group) is an international standard test protocol, mainly used for chip internal testing and system simulation and debugging. JTAG technology is an embedded test technology. All the components inside the chip can be accessed through the JTAG interface, which is a simple and efficient method for developing and debugging embedded systems. It has 2 connection standards, namely 14-pin interface and 20-pin interface. The standard of 14-pin interface is selected here. The JTAG interface circuit is shown as in Fig. 5.

Minimal system design based on S3C4510B microprocessor

After designing the above 4 parts of the circuit, S3C4510B has the basic conditions for safe and reliable operation.

3.2 Peripheral lead interface design

The design of the minimum system is for better research and development of microprocessors. Therefore, some necessary pins of the microprocessor should be led out with interface sockets to facilitate experimental development and use. The following will take the module as a unit to introduce the typical pins that need to be drawn, and give the selection of the corresponding circuit.

3.2.1 FLASH memory module

The required pin is ADDR[21:0], XDATA[31:0], NRCS0, nOE, nWBE0, nRESFT. The recommended circuit is TE28F320B produced by INTEL, with a storage capacity of 32M bits (4M bytes), a working voltage of 2.7V-3.6V, a 48-pin TSOP package or a 48-pin FBGA package, and a 16-bit data width.

3.2.2 SDRAM Module

The required pin is ADDR[21:0], XDATA[31:0], NSDCS0, nDWE, nSDRAS, nSDCAS, nWBE0, nWBE1, SDCLK, CKE. The recommended circuit is W986416DH from Winbond Company. Its storage capacity is 4 groups×16M bits (8M bytes), the working voltage is 3.3V, the common package is 54-pin TSOP, compatible with LVTTL interface, supports automatic refresh and self-refresh, 16-bit data width.

3.2.3 Ethernet interface module

The required pins are TX_ERR, TXD[3:0], TX_EN, TX_CLK, RX_ERR, RXD[3:0], RX_CLK, RX_DV, RX_ERR, nRESET, CRS, COL. The recommended interface circuit is DM9161 produced by Davicom. It is a single-port high-speed Ethernet physical layer interface circuit that can provide MII interface and traditional 7-wire network interface, and the working voltage is 3.3V.

3.2.4 I2C interface module

The required pins are SCL and SDA. Here, an AT24C01 produced by Atmel is expanded as the memory of the I2C interface module. Its working voltage is 5V and it can provide 128 bytes of EEPROM storage space for storing a small amount of data that needs to be saved when the system is powered off.

3.2.5 Real-time clock module

The required pins are E_ADDR3, SCL, SDA. The PCF8583 produced by Philips is a low-power CMOS real-time clock/calendar interface circuit with a working voltage of 3.3V and a built-in 256-byte SRAM. It communicates with the outside through the I2C interface. After each read and write operation is completed, The built-in address register will automatically increase.

3.2.6 ADC module

The required pins are E_ADDR0, E_ADDR1, E_ADDR2, E_nWBE0, E_nOE, nADC_CS, ADC_CLK. The ADC0809 produced by National Company is an 8-bit 8-channel successive approximation A/D converter with a working voltage of 5V. It has the characteristics of high speed, high precision, low temperature dependence and low power consumption.

3.2.7 DAC module

The required pin is E_D[7:0], NDAC_CS. The DAC0832 produced by National is an 8-bit CMOS D/A converter with a working voltage of 5V. It is composed of an 8-bit input register, an 8-bit DAC register, an 8-bit D/A converter, and a conversion control circuit. The 2-level register enables it to Realize multi-channel D/A synchronous conversion output.

3.2.8 General I/O Interface Module

Pins P0-P3 can be connected with jumpers to select high and low levels for status input or other input functions; pins P4-P7 can be connected with LEDs for Display of program running status or other output displays.

The above only lists the pins and circuits used by the 8 types of modules. In addition, there are serial interface modules, bus drive modules, decoding modules, LED/LCD Display modules, keyboard modules, etc., which are not listed one by one. The E_xxx pins mentioned above are all pins after bus driving and level conversion circuits. Such circuits include TI’s N74ALVC16245 (dual 8-channel), SN74LVC4245 (channel) and so on.

4 Hardware debugging

After the system is powered on, the output voltage of the power supply circuit is DC3.3V; the output frequency of the active crystal oscillator is 10MHz; the output terminal of the reset circuit (take the low-level active pin as an example) is output when the button is not pressed High level, low level after the button is pressed, and the output terminal returns to high level after the button is released.

Debug the S3C4510B through the JTAG interface. Before powering on, check whether the pin nEWAIT of the S3C4510B has been pulled up and the pin ExtMREQ has been pulled down. The processing of these two pins is related to whether the S3C4510B can work normally, and you must be very careful. After power-on, if the pin MCLKO/SDCLK ​​can output a 50MHz waveform with the on-chip PLL circuit enabled, it means that the S3C4510B has been working normally. At this point, you can use the integrated development tool ADS or SDT to access and control the components in the circuit through the JTAG interface. For example, by operating the special function register of the general I/O port inside the circuit to light up and connect to the P4-P7 ports If the LED can switch normally according to the setting of the register, it means that the minimum system designed is reliable.

5 concluding remarks

ARM microprocessor will compete with high-end MIPS and PowerPC embedded microprocessors with its excellent performance and extremely low power consumption. It is foreseeable that for a period of time in the future, ARM microprocessors will still dominate the 32-bit embedded microprocessor market. It is very necessary to learn and master ARB microprocessor technology, and designing ARM microprocessor to be the smallest system is an excellent way to learn this technology.

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