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# ch09 - 1 Chapter 9 Exercise Solutions E9.1 DTE stands for...

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Chapter 9 Exercise Solutions E9.1 DTE stands for data terminal equipment. Computers and terminals are examples of the DTE. DCE stands for data communication equipment. Modems and concentrators are examples of DCE. E9.2 A multi-drop serial communication uses a communication link that has one master and multiple slaves. E9.3 A communication link that is dedicated to either for transmission or receiving, but not both is called simplex link . A communication link that can be used for transmission or reception, but only in one direction at a time is called half-duplex link . A full-duplex link is a communication link that allows both transmission and reception to proceed simultaneously. E9.4 The voltage output between -5V and -25V is considered as mark (1). The voltage output between +5V and +25V is considered as space (0). E9.5 The ASCII code of the letter K is \$4B or %01001011. With even parity, the parity bit is 0. The TxD pin output will be as follows: 0 1 1 0 1 0 0 1 0 0 1 LSB MSB parity start bit stop bit E9.6 Using the format of 8 data bits, no parity, and 1 stop bit, ten bits are transmitted for every letter (a start bit is always required). For the speed of 4800 baud, the transmission of 1 bit takes 208.333 μ s. Thus the transmission of 100 characters will take 100 × 10 × 208.333 μ s = 208.333 ms E9.7 The SCI system use a clock signal with a frequency that is 16 times that of the data rate to sample the RxD pin signal. The majority function of the 8th, 9th, and 10th samples are used to determine the logic level of the data bit. E9.8 An easy way is to write a subroutine which simply calls the SCIputch subroutine in Example 9.6 until all the characters have been output. The SCIputst subroutine is as follows: SCIputst PSHA loop LDAA 0,Y ; get the next character from the string BEQ exit ; is this the NULL character? JSR SCIputch ; call the subroutine to output the character INY ; move the string pointer BRA loop 8- 1 1

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exit PULA RTS E9.9 To use the interrupt-driven method to output a string, we need to write two subroutines.
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ch09 - 1 Chapter 9 Exercise Solutions E9.1 DTE stands for...

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