EPROM PROGRAMMER DESIGN 8085 SOFTWARE

Three address lines of 8085 having specific value for a particular RAM are connected to the three select inputs (C, B and A) of 74LS138 decoder.

A0 вЂ“ A10 lines of 8085 are connected to 11 address lines of the RAM chips.

Table 10 shows the address range of the two chips. 18 shows the interfacing of IC 6264 with the 8085.Д®x: Interface two 6116 ICs with the 8085 using 74LS138 decoder such that the starting addresses assigned to them are 8000H and 9000H, respectively.Д¦116 has 11 address lines and since 2 KB, therefore ending addresses of 6116 chip 1 is and chip 2 are 87FFH and 97FFH, respectively. A NAND output of 0 selects the RAM chip for read or write operation, since CE2 is already 1 because of its connection to +5V. The NAND gate output is in turn connected to the ^(CE1) pin of the RAM chip. The NAND gate is designed such that when the lines A15 and A13 carry 0 and A14 carries 1, the output of the NAND gate is 0. When the address 4000H to 5FFFH are written in binary form, the values in the lines A15, A14, A13 are 0, 1 and 0 respectively. The ending address of the chip is 5FFFH (since 4000H + 1FFFH = 5FFFH). The memory address space of the 8085 takes values from 0000H to FFFFH.Д®x: Interface a 6264 IC (8K x 8 RAM) with the 8085 using NAND gate decoder such that the starting address assigned to the chip is 4000H. In the memory-mapped I/O scheme, each I/O device is assumed to be a memory location.ДЁ085 has 16 address lines (A0 - A15), hence a maximum of 64 KB (= 2 16В bytes) of memory locations can be interfaced with it. In the I/O mapped I/O scheme, the I/O devices are treated differently from memory. They can be interfaced using two schemes: I/O mapped I/O and memory-mapped I/O. Input and output devices, which are interfaced with 8085, are essential in any microprocessor based system.

EPROM PROGRAMMER DESIGN 8085 SOFTWARE

RAM can be used to store programs and data that include, programs written during software development for a microprocessor based system, program written when one is learning assembly language programming and data enter while testing these programs. In a RAM, stored programs and data are erased when the power supply to the chip is removed.

They can be used to store permanent programs.

Hence, they are called non-volatile memory. The programs and data that are stored in ROM/EPROM are not erased even when power supply to the chip is removed. The programs and data that are executed by the microprocessor have to be stored in ROM/EPROM and RAM, which are basically semiconductor memory chips. INTERFACING MEMORY AND I/O DEVICES WITH 8085

Eprom programmer design 8085