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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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M306V2EEFS датащи(PDF) 29 Page - Renesas Technology Corp |
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M306V2EEFS датащи(HTML) 29 Page - Renesas Technology Corp |
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29 / 271 page  Rev.1.40 Oct 06, 2004 page 29 of 269 M306V2ME-XXXFP, M306V2EEFP 2.4.4 Bus Control The following explains the signals required for accessing external devices and software waits. The sig- nals required for accessing the external devices are valid when the processor mode is set to memory expansion mode and microprocessor mode. The software waits are valid in all processor modes. (1) Address bus/data bus The address bus consists of the 20 pins A0 to A19 for accessing the 1M bytes of address space. The data bus consists of the pins for data I/O. When the BYTE pin is “H”, the 8 ports D0 to D7 function as the data bus. When BYTE is “L”, the 16 ports D0 to D15 function as the data bus. When a change is made from single-chip mode to memory expansion mode, the value of the address bus is undefined until external memory is accessed. (2) Chip select signal The chip select signal is output using the same pins as P44 to P47. Bits 0 to 3 of the chip select control register (address 000816) set each pin to function as a port or to output the chip select signal. The chip select control register is valid in memory expansion mode and microprocessor mode. In single-chip mode, P44 to P47 function as programmable I/O ports regardless of the value in the chip select control register. _______ In microprocessor mode, only CS0 outputs the chip select signal after the reset state has been can- _______ _______ celled. CS1 to CS3 function as input ports. Figure 2.4.4 shows the chip select control register. The chip select signal can be used to split the external area into as many as four blocks. Table 2.4.4 shows the external memory areas specified using the chip select signal. Chip select Specified address range Memory expansion mode Microprocessor mode 3000016 to 8FFFF16 (384K) CS0 CS1 CS2 CS3 2800016 to 2FFFF16 (32K) 0800016 to 27FFF16 (128K) 0400016 to 07FFF16 (16K) 3000016 to 8FFFF16 (384K), B0000 16 to FFFFF16 (320K) 2800016 to 2FFFF16 (32K) 0800016 to 27FFF16 (128K) 0400016 to 07FFF16 (16K) Table 2.4.3 External areas specified by the chip select signals |
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