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CR16MCS9VJI80 Datasheet(PDF) 5 Page - National Semiconductor (TI) |
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CR16MCS9VJI80 Datasheet(HTML) 5 Page - National Semiconductor (TI) |
5 / 156 page 5 www.national.com 3.0 Device Overview The devices are complete microcomputers with all system timing, interrupt logic, program memory, data memory, and I/ O ports included on-chip, making it well-suited to a wide range of embedded controller applications. 3.1 CR16B CPU CORE The device uses a CR16B CPU core module. This is the same core used in other CompactRISC family member de- signs, like DECT or GSM chipsets. The high performance of the CPU core results from the im- plementation of a pipelined architecture with a two-bytes-per- cycle pipelined system bus. As a result, the CPU can support a peak execution rate of one instruction per clock cycle. Compared with conventional RISC processors, the device differs in the following ways: — The CPU core can use on-chip rather than external memory. This eliminates the need for large and com- plex bus interface units. — Most instructions are 16 bits, so all basic instructions are just two bytes long. Additional bytes are sometimes required for immediate values, so instructions can be two or four bytes long. — Non-aligned word access is allowed. Each instruction can operate on 8-bit or 16-bit data. — The device is designed to operate with a clock rate in the 10 to 24 MHz range rather than 100 MHz or more. Most embedded systems face EMI and noise con- straints that limit clock speed to these lower ranges. A lower clock speed means a simpler, less costly silicon implementation. — The instruction pipeline uses three stages. A smaller pipeline eliminates the need for costly branch predic- tion mechanisms and bypass registers, while maintain- ing adequate performance for typical embedded controller applications. For more information, please refer to the CR16B Program- mer’s Reference Manual, Literature #: 633150. 3.2 MEMORY The CompactRISC architecture supports a uniform linear ad- dress space of 2 megabytes. The device implementation of this architecture uses only the lowest 128K bytes of address space. Four types of on-chip memory occupy specific inter- vals within this address space: • 64K bytes of flash EEPROM program memory (100K cy- cles) • 48K bytes ROM programm memory version available also (100K cycles) • 3K bytes of static RAM • 2K bytes of EEPROM data memory with low endurance (25K cycles) • 128 bytes with high endurance (100K cycles) • 1.5K bytes flash EEPROM memory for ISP code The 3K bytes of static RAM are used for temporary storage of data and for the program stack and interrupt stack. Read and write operations can be byte-wide or word-wide, depend- ing on the instruction executed by the CPU. Each memory access requires one clock cycle; no wait cycles or hold cycles are required. There are two types of flash EEPROM data memory storage. The 2K bytes of EEPROM data memory with low endurance (25K cycles) and 128 bytes of flash EEPROM data memory with high endurance (100K cycles) are used for non-volatile storage of data, such as configuration settings entered by the end-user. The 64K bytes of flash EEPROM program memory are used to store the application program. It has security features to prevent unintentional programming and to prevent unautho- rized access to the program code. This memory can be pro- grammed with a device external programming unit or with the device installed in the application system (in-system pro- gramming). There is a factory programmed boot memory used to store In-System-Programming (ISP) code. (This code allows pro- gramming of the program memory via one of the USART in- terfaces in the final application.) For flash EEPROM program and data memory, the device in- ternally generates the necessary voltages for programming. No additional power supply is required. 3.3 INPUT/OUTPUT PORTS The device has 56 software-configurable I/O pins, organized into seven 8-pin ports called Port B, Port C, Port F, Port G, Port H, Port I, and Port L. Each pin can be configured to op- erate as a general-purpose input or general-purpose output. In addition, many I/O pins can be configured to operate as a designated input or output for an on-chip peripheral module such as the USART, timer, A/D converter, or MICROWIRE/ SPI interface. The I/O pin characteristics are fully programmable. Each pin can be configured to operate as a TRI-STATE output, push- pull output, weak pull-up input, or high-impedance input. 3.4 BUS INTERFACE UNIT The Bus Interface Unit (BIU) controls the interface between the on-chip modules to the internal core bus. It determines the configured parameters for bus access (such as the num- ber of wait states for memory access) and issues the appro- priate bus signals for each requested access. The BIU uses a set of control registers to determine how many wait states and hold states are to be used when ac- cessing flash EEPROM program memory, ISP memory and the I/O area (Port B and Port C). Upon start-up the configu- ration registers are set for slowest possible memory access. To achieve fastest possible program execution, appropriate values should be programmed. These settings vary with the clock frequency and the type of on-chip device being access- ed. |
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