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ISL12059IBZ bảng dữ liệu(PDF) 7 Page - Intersil Corporation |
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ISL12059IBZ bảng dữ liệu(HTML) 7 Page - Intersil Corporation |
7 / 11 page 7 FN6757.0 June 15, 2009 Accuracy of the Real Time Clock The accuracy of the Real Time Clock depends on the frequency of the quartz crystal that is used as the time base for the RTC. Since the resonant frequency of a crystal is temperature dependent, the RTC performance will also be dependent upon temperature. The frequency deviation of the crystal is a function of the turnover temperature of the crystal from the crystal’s nominal frequency. For example, a ~20ppm frequency deviation translates into an accuracy of ~1 minute per month. These parameters are available from the crystal manufacturer. I2C Serial Interface The ISL12059 has an I2C serial bus interface that provides access to the real time clock registers, and control and status registers. The I2C serial interface is compatible with other industry I2C serial bus protocols using a bi-directional data signal (SDA) and a clock signal (SCL). Register Descriptions The registers are accessible following a slave byte of “1101000x” and reads or writes to addresses [00h:07h]. The defined addresses and default values are described in Table 1. REGISTER ACCESS The contents of the registers can be modified by performing a byte or a page write operation directly to any register address. The address will wrap around from 07h to 00h. The registers are divided into 2 sections. These are: 1. Real Time Clock (7 bytes): Address 00h to 06h. 2. Control and Status (1 byte): Address 07h. There are no addresses above 07h. A register can be read by performing a random read at any address at any time. This returns the contents of that register location. Additional registers are read by performing a sequential read. For the RTC registers, the read instruction latches all clock registers into a buffer, so an update of the clock does not change the time being read. A sequential read will not result in the output of data from the memory array. At the end of a read, the master supplies a stop condition to end the operation and free the bus. After a read or write instruction, the address remains at the previous address +1 so the user can execute a current address read and continue reading the next register. Real Time Clock Registers Addresses [00h to 06h] RTC REGISTERS (SC, MN, HR, DW, DT, MO, YR) These registers depict BCD representations of the time. As such, SC (Seconds, address 00h) and MN (Minutes, address 01h) range from 0 to 59, HR (Hour, address 02h) is in a 24-hour mode with a range from 0 to 23, DW (Day of the Week, address 03h) is 0 to 6, DT (Date, address 04h) is 1 to 31, MO (Month, address 05h) is 1 to 12, and YR (Year, address 06h) is 0 to 99. The DW register provides a Day of the Week status and uses three bits DW2 to DW0 to represent the seven days of the week. The counter advances in the cycle 1-2-3-4-5-6-7-1-2-… The assignment of a numerical value to a specific day of the week is arbitrary and may be decided by the system software designer. Bit D7 of SC register contain the crystal enable/disable bit (ST). Setting ST to “1” will disable the crystal from oscillating and stop the counting in RTC register for the device to enter into power saving mode. The ST bit is set to “0” on power-up for normal operation. Bit D7 of MN register contain the Oscillator Fail Indicator bit (OF). This bit is set to a “1” when there is no oscillation on X1 pin. The OSF bit can only be reset by having an oscillation on X1 and a write operation to reset it. Bits D6 and D7 of HR register (century/hours register) contain the century enable bit (CEB) and the century bit (CB). Setting CEB to a '1' will cause CB to toggle, either from '0' to '1' or from '1' to '0' at the turn of the century (depending upon its initial state). If CEB is set to a '0', CB will not toggle. TABLE 1. REGISTER MEMORY MAP ADDR. SECTION REG NAME BIT REG 7 6 543210 RANGE DEFAULT 00h RTC SC ST SC22 SC21 SC20 SC13 SC12 SC11 SC10 0 to 59 00h 01h MN OF MN22 MN21 MN20 MN13 MN12 MN11 MN10 0 to 59 80h 02h HR CEB CB HR21 HR20 HR13 HR12 HR11 HR10 0 to 23 00h 03h DW 0 0 0 0 0 DW12 DW11 DW10 1 to 7 01h 04h DT 0 0 DT21 DT20 DT13 DT12 DT11 DT10 1 to 31 01h 05h MO 0 0 0 MO20 MO13 MO12 MO11 MO10 1 to 12 01h 06h YR YR23 YR22 YR21 YR20 YR13 YR12 YR11 YR10 0 to 99 00h 07h Control FT/OUT OUT FT 00000 PF N/A 81h ISL12059 |
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