DS12887 RTC Interfacing and Programming - Unit 16 - Review Questions & Answers from 8051 Microcontrollers & Embedded Systems by Mazidi

SECTION 16.1: DS12887 RTC INTERFACING

1. True or false. All of the RAM contents of the DS12887 are nonvolatile.

2. How many bytes of RAM in the DS12887 are set aside for the clock and date? 

3. How many bytes of RAM in the DS12887 are set aside for general-purpose applications?

4. True or false. The NV-RAM contents of the DS12887 can last up to 10 years without an external power source. 

5. Which pin of the DS12887 is the same as the ALE pin in the 8051?

6. True or false. When the DS12887 is shipped, its oscillator is turned on. 

Answers: 

1. True 

2. 9

3. 114

4. True

5. AS 

6. False 

SECTION 16.2: DS12887 RTC PROGRAMMING IN C 

1. True or false. The time and date are not updated during the initialization of RTC.

2. What address range is used for the time and date? 

3. Give the address of the first RAM location belonging to general-purpose applications.

4. Give the C statement to set the month to October. 

5. Give the C statement to set the year to 2009. 

Answers: 

1. True 

2. 0-9

3. 0EH (14 in decimal)

4. XBYTE[8]=0xOA;

5. XBYTE[09]=0x09; where the 20 part of 2009 is assumed.

SECTION 16.3: ALARM, SQW, AND IRQ FEATURES OF THE DS12887 CHIP 

1. Which bit of register B belongs to the SQW pin?

2. True or false. The IRQ out pin of DS12887 is active low. 

3. Which bit of register B belongs to alarm interrupt?

4. Give the address locations for hh:mm:ss of the alarm. 

5. If the source of activation for IRQ is alarm, then explain how the IRQ pin is activated.

6. What is the difference between the AF and AIE bits? 

7. What is the difference between the PF and PIE bits? 

Answers: 

1. D3 of D0 - D7 

2. True 

3. D5

4. Byte addresses of 1, 3, 5

5. If the AIE bit of Reg B is set to 1, then the IRQ pin is activated. This happens due to the AF bit in register C going high when the alarm time and real time values match.

6. The AF bit in register C becomes high when the alarm time and real time values match, while the AIE bit of register B simply allows the AF to be directed to the IRQ pin.

7. The PF bit in register C becomes high when the edge is detected for the periodic interrupt, while the PIE bit of reg­ister B simply allows the PF to be directed to the IRQ pin.