from a decoder with unused address lines as its input. In the present example, address lines An+1 to A15 may
be used for generating the chip-select signal.
As illustrated in Fig. 17.4, the PSEN
signal from the processor may directly be used as the read input for pro-
gram memory. e de-multiplexer ‘octal latch’ is used to generate the lower address signals, A0–A7, with the help of
ALE output from the processor. Data output lines from program memory are directly connected with AD0–AD7
pins of the processor. e EA input is pulled up to ensure external program memory access after completion of ac-
cessing internal ...
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