In the HT48XA0-2 and HT48XA0-1 series of devices when “0” is written to bit 7~6 of the memory pointer MP, when it is read out, why does it give a value of “1”?
Answer The HT48XA0-2, HT48XA0-1 Data RAM address are located at the address range 20H~3FH. Because the data RAM capacity does not exceed 40H, a 6-bit memory pointer (Bit0~Bit5) is adequate. Reading bit 7 or 6 of MP will always give a value of “1” irrespective of what value has been written into it. If the value “20H” is written to MP it will be read back as “E0H” but in fact the actual address pointed to is “20H” which is correct for the indirect addressing operations.
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