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Timekeeping Registers

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logic edited this page Mar 16, 2011 · 11 revisions

Timekeeping Registers

Timekeeping registers from a variety of DS/Maxim RTC ICs.

Complete list of DS RTC ICs.

All DS devices have an I²C address that derives from 0b1101000 (0x68); additional functionality, such as EEPROM or FRAM storage, is typically presented in separately-addressable 256-byte blocks (ie. as 0x69, 0x6A, etc).

DS1307

64 x 8, Serial, I²C Real-Time Clock

Applies to: DS1307

Datasheet

ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION RANGE
00h CH 10 Seconds Seconds Seconds 00-59
01h 0 10 Minutes Minutes Minutes 00-59
02h 0 12/24 AM/PM 10 Hour Hours Hours 1-12 +AM/PM 00-23
10 Hour
03h 0 0 0 0 0 Day Day 01-07
04h 0 0 10 Date Date Date 01-31
05h 0 0 0 10 Month Month Month 01-12
06h 10 Year Year Year 00-99
07h OUT 0 0 SQWE 0 0 RS1 RS0 Control  
08h-3Fh   RAM 56 x 8 00h-FFh

DS1337

I²C Serial Real-Time Clock

Applies to: DS1337, DS1337C

Datasheet

ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION RANGE
00h 0 10 Seconds Seconds Seconds 00-59
01h 0 10 Minutes Minutes Minutes 00-59
02h 0 12/24 AM/PM 10 Hour Hours Hours 1-12 +AM/PM 00-23
10 Hour
03h 0 0 0 0 0 Day Day 01-07
04h 0 0 10 Date Date Date 01-31
05h Century 0 0 10 Month Month Month/Century 01-12
06h 10 Year Year Year 00-99
07h A1M1 10 Seconds Seconds Alarm 1 Seconds 00-59
08h A1M2 10 Minutes Minutes Alarm 1 Minutes 00-59
09h A1M3 12/24 AM/PM 10 Hour Hours Alarm 1 Hours 1-12 +AM/PM 00-23
10 Hour
0Ah A1M4 DY/DT 0 0 0 Day Alarm 1 Day 1-7
Date Alarm 1 Date 01-31
0Bh A2M2 10 Minutes Minutes Alarm 2 Minutes 00-59
0Ch A2M3 12/24 AM/PM 10 Hour Hours Alarm 2 Hours 1-12 +AM/PM 00-23
10 Hour
0Dh A2M4 DY/DT 0 0 0 Day Alarm 2 Day 1-7
Date Alarm 2 Date 01-31
0Eh EOSC 0 0 RS2 RS1 INTCN A2IE A1IE Control  
0Fh OSF 0 0 0 0 0 A2F A1F Status  

DS1338

I²C RTC with 56-Byte NV RAM

Applies to: DS1338, DS1338C, DS1338U, DS1338Z

Datasheet

Notes: functionally identical to DS1307 except for addition of OSF (Oscillator Stop Flag) bit in the control register.

ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION RANGE
00h CH 10 Seconds Seconds Seconds 00-59
01h 0 10 Minutes Minutes Minutes 00-59
02h 0 12/24 AM/PM 10 Hour Hours Hours 1-12 +AM/PM 00-23
10 Hour
03h 0 0 0 0 0 Day Day 01-07
04h 0 0 10 Date Date Date 01-31
05h 0 0 0 10 Month Month Month 01-12
06h 10 Year Year Year 00-99
07h OUT 0 OSF SQWE 0 0 RS1 RS0 Control  
08h-3Fh   RAM 56 x 8 00h-FFh

DS1339

I²C Serial Real-Time Clock

Applies to: DS1339, DS1339C, DS1339U

Datasheet

Notes: functionally identical to DS1337 except for addition of BBSQI bit in the control register, and trickle charger register.

ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION RANGE
00h 0 10 Seconds Seconds Seconds 00-59
01h 0 10 Minutes Minutes Minutes 00-59
02h 0 12/24 AM/PM 10 Hour Hours Hours 1-12 +AM/PM 00-23
10 Hour
03h 0 0 0 0 0 Day Day 01-07
04h 0 0 10 Date Date Date 01-31
05h Century 0 0 10 Month Month Month/Century 01-12
06h 10 Year Year Year 00-99
07h A1M1 10 Seconds Seconds Alarm 1 Seconds 00-59
08h A1M2 10 Minutes Minutes Alarm 1 Minutes 00-59
09h A1M3 12/24 AM/PM 10 Hour Hours Alarm 1 Hours 1-12 +AM/PM 00-23
10 Hour
0Ah A1M4 DY/DT 0 0 0 Day Alarm 1 Day 1-7
Date Alarm 1 Date 01-31
0Bh A2M2 10 Minutes Minutes Alarm 2 Minutes 00-59
0Ch A2M3 12/24 AM/PM 10 Hour Hours Alarm 2 Hours 1-12 +AM/PM 00-23
10 Hour
0Dh A2M4 DY/DT 0 0 0 Day Alarm 2 Day 1-7
Date Alarm 2 Date 01-31
0Eh EOSC 0 BBSQI RS2 RS1 INTCN A2IE A1IE Control  
0Fh OSF 0 0 0 0 0 A2F A1F Status  
10h TCS3 TCS2 TCS1 TCS0 DS1 DS0 ROUT1 ROUT0 Trickle Charger  

DS1340

Low-Current I²C RTCs for High-ESR Crystals

Applies to: DS1340, DS1340C

Datasheet

Notes: Similar to DS1307.

  • EOSC (Enable Oscillator) is now at register 0x00 bit 7 instead of CH.
  • CEB (Century Enable Bit) added at 0x02 bit 7
  • CB (Century Bit) is now at 0x02 bit 6 instead of 12/24 switch.
  • Control register has changed significantly.
  • Trickle Charger register added.
  • OSF (Oscillator Stop Flag) added, in new Flag register.
ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION RANGE
00h EOSC 10 Seconds Seconds Seconds 00-59
01h 0 10 Minutes Minutes Minutes 00-59
02h CEB CB 10 Hours Hours Century/Hours 0-1; 00-23
03h 0 0 0 0 0 Day Day 01-07
04h 0 0 10 Date Date Date 01-31
05h 0 0 0 10 Month Month Month 01-12
06h 10 Year Year Year 00-99
07h OUT FT S CAL4 CAL3 CAL2 CAL1 CAL0 Control  
08h TCS3 TCS2 TCS1 TCS0 DS1 DS0 ROUT1 ROUT0 Trickle Charger  
09h OSF 0 0 0 0 0 0 0 Flag  

DS1341, DS1342

Low-Current I²C RTCs for High-ESR Crystals

Applies to: DS1341, DS1342

Datasheet

Notes: Similar to DS1337, with differences in control and status registers.

  • EGFIL (Enable Glitch Filter) added to control register
  • DOSF (Disable Oscillator Stop Flag), LOS (Loss Of Signal), CLKSEL1/2 (Select Clock Source), and ECLK (Enable External Clock Input) added to control/status register.
ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION RANGE
00h 0 10 Seconds Seconds Seconds 00-59
01h 0 10 Minutes Minutes Minutes 00-59
02h 0 12/24 AM/PM 10 Hour Hours Hours 1-12 +AM/PM 00-23
10 Hour
03h 0 0 0 0 0 Day Day 01-07
04h 0 0 10 Date Date Date 01-31
05h Century 0 0 10 Month Month Month/Century 01-12
06h 10 Year Year Year 00-99
07h A1M1 10 Seconds Seconds Alarm 1 Seconds 00-59
08h A1M2 10 Minutes Minutes Alarm 1 Minutes 00-59
09h A1M3 12/24 AM/PM 10 Hour Hours Alarm 1 Hours 1-12 +AM/PM 00-23
10 Hour
0Ah A1M4 DY/DT 0 0 0 Day Alarm 1 Day 1-7
Date Alarm 1 Date 01-31
0Bh A2M2 10 Minutes Minutes Alarm 2 Minutes 00-59
0Ch A2M3 12/24 AM/PM 10 Hour Hours Alarm 2 Hours 1-12 +AM/PM 00-23
10 Hour
0Dh A2M4 DY/DT 0 0 0 Day Alarm 2 Day 1-7
Date Alarm 2 Date 01-31
0Eh EOSC 0 EGFIL RS2 RS1 INTCN A2IE A1IE Control  
0Fh OSF DOSF LOS CLKSEL2 CLKSEL1 ECLK A2F A1F Control/Status  

DS1371

I²C, 32-Bit Binary Counter Watchdog Clock

Applies to: DS1371

Datasheet

ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION
00h TOD COUNTER BYTE 0 Time-of-Day Counter
01h TOD COUNTER BYTE 1 Time-of-Day Counter
02h TOD COUNTER BYTE 2 Time-of-Day Counter
03h TOD COUNTER BYTE 3 Time-of-Day Counter
04h WD/ALM COUNTER BYTE 0 Watchdog/Alarm Counter
05h WD/ALM COUNTER BYTE 1 Watchdog/Alarm Counter
06h WD/ALM COUNTER BYTE 2 Watchdog/Alarm Counter
07h EOSC WACE WD/ALM 0 INTCN RS2 RS1 AIE Control
08h OSF 0 0 0 0 0 0 AF Status

DS1372

I²C, 32-Bit, Binary Counter Clock with 64-Bit ID

Applies to: DS1372

Datasheet

ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION
00h   Seconds Counter Byte 0 LSB Clock
01h   Seconds Counter Byte 1   Clock
02h   Seconds Counter Byte 2   Clock
03h MSB Seconds Counter Byte 3   Clock
04h   Alarm Counter Byte 0 LSB Alarm
05h   Alarm Counter Byte 1   Alarm
07h MSB Alarm Counter Byte 2   Alarm
07h EOSC ACE 0 0 INTCN RS2 RS1 AIE Control
08h OSF 0 0 0 0 0 0 AF Status
09h Model Number ID
0Ah Serial Number Byte 0 ID
0Bh Serial Number Byte 1 ID
0Ch Serial Number Byte 2 ID
0Dh Serial Number Byte 3 ID
0Eh Serial Number Byte 4 ID
0Fh Serial Number Byte 5 ID
10h CRC ID

DS1374

I²C, 32-Bit Binary Counter Watchdog RTC with Trickle Charger and Reset Input/Output

Applies to: DS1374, DS1374C, DS1374U

Datasheet

Notes: Same as DS1371, with added trickle charger register and BSSQE bit in control register.

ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION
00h TOD COUNTER BYTE 0 Time-of-Day Counter
01h TOD COUNTER BYTE 1 Time-of-Day Counter
02h TOD COUNTER BYTE 2 Time-of-Day Counter
03h TOD COUNTER BYTE 3 Time-of-Day Counter
04h WD/ALM COUNTER BYTE 0 Watchdog/Alarm Counter
05h WD/ALM COUNTER BYTE 1 Watchdog/Alarm Counter
06h WD/ALM COUNTER BYTE 2 Watchdog/Alarm Counter
07h EOSC WACE WD/ALM BBSQW INTCN RS2 RS1 AIE Control
08h OSF 0 0 0 0 0 0 AF Status
09h TCS3 TCS2 TCS1 TCS0 DS1 DS0 ROUT1 ROUT0 Trickle Charger

DS1375

I²C Digital Input RTC with Alarm

Applies to: DS1375

Datasheet

Notes: similar to DS1337, with significant differences in control/status registers and addition of SRAM.

ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION RANGE
00h 0 10 Seconds Seconds Seconds 00-59
01h 0 10 Minutes Minutes Minutes 00-59
02h 0 12/24 AM/PM 10 Hours Hours Hours 1-12 +AM/PM 00-23
10 Hours
03h 0 0 0 0 0 Day Day 01-07
04h 0 0 10 Date Date Date 01-31
05h Century 0 0 10 Month Month Month/Century 01-12
06h 10 Year Year Year 00-99
07h A1M1 10 Seconds Seconds Alarm 1 Seconds 00-59
08h A1M2 10 Minutes Minutes Alarm 1 Minutes 00-59
09h A1M3 12/24 AM/PM 10 Hours Hours Alarm 1 Hours 1-12 +AM/PM 00-23
10 Hours
0Ah A1M4 DY/DT   Day Alarm 1 Day 1-7
10 Date Date Alarm 1 Date 01-31
0Bh A2M2 10 Minutes Minutes Alarm 2 Minutes 00-59
0Ch A2M3 12/24 AM/PM 10 Hour Hours Alarm 2 Hours 1-12 +AM/PM 00-23
10 Hour
0Dh A2M4 DY/DT   Day Alarm 2 Day 1-7
10 Date Date Alarm 2 Date 01-31
0Eh ECLK CLKSEL1 CLKSEL0 RS2 RS1 INTCN A2IE A1IE Control  
0Fh 0 0 0 0 0 0 A2F A1F Control/Status  
10h-1Fh   SRAM 00-FFh

DS1388

I²C RTC/Supervisor with Trickle Charger and 512 Bytes EEPROM

Applies to: DS1388

Datasheet

Notes: somewhat of a "black sheep".

  • three blocks of memory: 0x00 for typical registers, 0x01 and 0x02 for EEPROM
  • prior to typical RTC clock information, a "hundredths of seconds" register has been added, and RTC clock registers are all incremented by one memory address
  • EEPROM is presented as separate addresses on the I2C bus; the base address is 0b1101, followed by three bits indicating the block to interact with, followed by a read/write bit (1=read, 0=write).
  • two bits are provided as general-purpose toggles (X).
BLOCK ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION RANGE
0 00h Tenth Seconds Hundredths of Seconds Hundredths of Seconds 00-99
01h 0 10 Seconds Seconds Seconds 00-59
02h 0 10 Minutes Minutes Minutes 00-59
03h 0 12/24 AM/PM 10 Hour Hours Hours 1-12 +AM/PM 00-23
10 Hour
04h 0 0 0 0 X Day Day 01-07
05h 0 0 10 Date Date Date 01-31
06h Century 0 X 10 Month Month Month/Century 01-12
07h 10 Year Year Year 00-99
08h Watchdog Tenths of Seconds Watchdog Hundredths of Seconds Watchdog Hundredth Seconds 00-99
09h Watchdog Tenths of Seconds Watchdog Seconds Watchdog Seconds 00-59
0Ah TCS3 TCS2 TCS1 TCS0 DS1 DS0 ROUT1 ROUT0 Trickle Charger  
0Fh OSF WF 0 0 0 0 0 0 Flag  
10h EOSC 0 0 0 0 0 WDE WD/RST Control  
1 00h-FFh 256 x 8 EEPROM EEPROM 00-FFh
2 00h-FFh 256 x 8 EEPROM EEPROM 00-FFh
0 = always reads as zero X = General-purpose r/w bit
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