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P80C51HFP Datasheet(PDF) 6 Page - NXP Semiconductors |
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P80C51HFP Datasheet(HTML) 6 Page - NXP Semiconductors |
6 / 40 page Philips Semiconductors Product specification 80CL31/80CL51 Low-voltage single-chip 8-bit microcontrollers January 1995 6 1.0 FUNCTIONAL DESCRIPTION General The 80CL51 is a stand-alone high-performance CMOS microcontroller designed for use in real-time applications such as instrumentation, industrial control, intelligent computer peripherals and consumer products. The device provides hardware features, architectural enhancements and new instructions to function as a controller for applications requiring up to 64K bytes of program memory and/or up to 64K bytes of data storage. The 80CL51 contains a non-volatile 4K byte × 8 read-only program memory; a static 128 byte × 8 read/write data memory; 32 1/0 lines; two 16-bit timer/event counters; a thirteen- source two priority-level, nested interrupt structure and on-chip oscillator and timing circuit. The device has two software selectable modes of reduced activity for power reduction: IDLE and Power-down. The Idle mode freezes the CPU while allowing the RAM, timers, serial I/O and interrupt system to continue functioning. The Power-down mode saves the RAM contents but freezes the oscillator causing all other chip functions to be inoperative. The P80C51 is a 5V version of the low voltage microcontroller P80CL51. Hereafter the generic term P80CL51 will be used for the functional description of both types. The special features of the P80C51 are handled in chapter 1.9. CPU timing A machine cycle consists of a sequence of 6 states. Each state time lasts for two oscillator periods, thus a machine cycle takes 12 oscillator periods or 1 µs if the oscillator frequency is 12MHz. 1.1 Memory organization The 80CL51 has a 4K Program Memory (ROM) plus 128 bytes of Data Memory (RAM) on board. The device has separate address spaces for Program and Data Memory (see Memory Map). Using Ports P0 and P2, the 80CL51 can address up to 64K bytes of external memory. The CPU generates both read and write signals (RD and WR) for external Data Memory accesses, and the read strobe (PSEN) for external Program Memory. 1.1.1 Program Memory The 80CL51 contains 4K bytes of internal ROM. After reset the CPU begins execution at location 0000H. The lower 4K bytes of Program Memory can be implemented in either on- chip ROM or external Memory. If the EA pin is strapped to VDD, then program memory fetches from addresses 000H through 0FFFH are directed to the internal ROM. Fetches from addresses 1000H through FFFFH are directed to external ROM. Program counter values greater than 0FFFH are automatically addressed to external memory regardless of the state of the EA pin. 1.1.2 Data Memory The 80CL51 contains 128 bytes of internal RAM and 25 Special Function Registers (SFR). The Memory Map below shows the internal Data Memory space divided into the Lower 128, the Upper 128, and the SFR space. The lower 128 bytes of the internal RAM are organized as mapped in Figure 1. The lowest 32 bytes are grouped into 4 banks of 8 registers. Program instructions refer to these registers R0 through R7. Two bits in the Program Status Word select which register bank is in use. The next 16 bytes above the register banks form a block of bit-addressable memory space. The 128 bits in this area can be directly addressed by the single-bit manipulation instructions. The remaining registers (30H to 7FH) are directly and indirectly byte addressable. 1.1.3 Special Function Registers The upper 128 bytes are the address locations of the SFRs. Figure 2 shows the Special Function Register (SFR) space. SFRs include the port latches, timers, peripheral control, serial I/O registers, etc. These registers can only be accessed by direct addressing. There are 128 addressable locations in the SFR address space (SFRs with addresses divisible by eight). 1.1.4 Addressing The 80CL51 has five methods for addressing source operands: – Register – Direct – Register-lndirect – Immediate – Base-Register-plus Index-Register-indirect MEMORY MAP SPECIAL FUNCTION REGISTERS 64K EXTERNAL 4096 4095 4095 INTERNAL (EA = 0) INTERNAL (EA = 1) 225 127 0 INTERNAL DATA RAM OVERLAPPED SPACE 64K 0 EXTERNAL DATA RAM INTERNAL DATA MEMORY PROGRAM MEMORY |
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