The addresses assigned to 6 registers of the I / O interface of Figure 11-2 are equal to the hexadecimal equivalent of 23, 24, 25, 26, 27 and 28. Show the external circuit to be connected between the address of I / O of 8 bits of the CPU and the inputs CS, RS1, and RS0 of the interface .

L/O data Port A register us buffers data bus L/0 data Port B register Chip select CS RSI RSO Timing Register select Control Control register and I/0 read RD control write WR Status Status register To CPU To I/0 device CS RSI RSORegister selected 0 x xNone: data bus in high-impedance 1 0 0 Port A register 1 0 Port B register 10 Control register 1 Status register Figure 11-2 Example of VO interface unit