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A smart home control module with 8 switches and associated registers is connected as an input device through an I/O interface board to the MC68HC11...

A smart home control module with 8 switches and associated registers is connected as an input device through an I/O interface board to the MC68HC11 microcontroller. After the microcontroller requests to perform a READ operation on the smart home control module, the ON/OFF status of each switch (S0 - S7) denoted as 1/0 will be updated to the data buffer register (DBR) of the I/O interface board. S7 will be loaded into the MSB (bit 7) of DBR while S0 will be loaded into its LSB (bit 0) during each update. For instance, if S7 is ON while the remaining switches (S0 - 6) are OFF, the updated content of DBR should be: 100000002. For any input device, the control/status register (CSR) and DBR of the I/O interface board is assigned to memory address $8004 and $8006 respectively. The command code to perform a READ operation on the smart home control module is $28.

(a) Clearly explain the detailed steps with an illustrative diagram to load 1 byte of data from the DBR of the I/O interface board to the Accumulator B of the MC68HC11 microcontroller using the programmed I/O mechanism.   

(b) Assume switches S6, S5, S3 and S1 are ON and the remaining are OFF at the moment, after applying the programmed I/O mechanism described in (a), what are the resulting contents of Accumulator A and B?

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