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V3020TP8B Datasheet(PDF) 13 Page - EM Microelectronic - MARIN SA |
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V3020TP8B Datasheet(HTML) 13 Page - EM Microelectronic - MARIN SA |
13 / 17 page R V3020 Copyright © 2005, EM Microelectronic-Marin SA 13 www.emmicroelectronic.com Reading the Current Time and Date Send copy_clock_to_RAM addr. F hex Read time and data status bits, addr. 1 Is the seconds status bit set, addr. 1, bit 0 Read seconds, addr. 2 Is the minutes status bit set, addr. 1, bit 1 Read minutes, addr. 3 Similar for hours, day of month, week day, month, year and week number No No Yes Yes Current time and date Fig. 11 Clock and Calendar The Time and date addresses in the RAM (see Table 6) provide access to the seconds, minutes, hours, day of month, month, year, week day, and week number. These parameters have the ranges indicated on Table 6 and are in BCD format. If a parameter is found to be out of range, it will be cleared on its being next incremented. The V3020 incorporates leap year correction and week number calculation. The week number changes only at the incrementation of the day number from 7 to 1. If week 52 day 7 falls on the 25 th, 26th or 27th of December, then the week number will change to 0, otherwise it will be week 1. Week days are numbered from 1 to 7 with Monday as 1. Reading of the current time and date must be preceded by a Copy_clock_to_RAM command. The time and date status bits will indicate which time and date addresses changed since the last time the command was used (see Fig. 11). The time and date from the last Copy_clock_to_RAM command is held unchanged in the RAM, except when power (VDD) has failed totally. To change the current time and date in the clock, the desired time an date must first be written to the RAM, the time set lock bit cleared, and then a Copy_RAM_to_clock command sent (see Fig. 12). The time set lock bit can be used to prevent unauthorized setting of the clock. Setting the Current Time and Date Write seconds, minutes, hours, day of month, week day, month, year and week number to the RAM Clear the time set lock bit, addr. 0, bit 4 Send copy_RAM_to_clock command, addr. E hex Set the time set lock bit, addr. 0, bit 4 Fig. 12 Frequency Measurement Setting bit 0 at address 0 will put a pulsed current source (25 µA) onto the I/O pin, when the device is not chip selected (ie. CS input high). The current source will be pulsed on/off at 256 Hz. The period for ± 0 ppm time keeping is 3.90625 ms. To measure the frequency signal on pin I/O, the data bus must be high impedance. The best way to ensure this is to hold the microprocessor and peripherals in reset mode while measuring the frequency. The clarity of the signal measured at pin I/O will depend on both the probe input impedance (typically 1 M Ω) and the magnitude of the leakage current from other devices driving the line connected to pin I/O. If the signal measured is unclear, put a 200 k Ω resistor from pin I/O to VSS. It should be noted that the magnitude of the current source (25 µA) is not sufficient to drive the data bus line in case of any other device driving the line, but it is sufficient to take the line to a high logic level when the data bus is in high impedance. Use a crystal of nominal CL = 8.2 pF as specified in the section "Operating Conditions". The MX series from Microcrystal is recommended. The accuracy of the time keeping is dependent upon the frequency tolerance and the load capacitance of the crystal. 11.57 ppm corresponds to one second a day. Test From the various test features added to the V3020 some may be activated by the user. Table 7a shows the test mode b its. Table 8 shows the 3 available test modes and how they can be activated. Test mode 0 is activated by setting bit 2, address 0, and causes all time keeping to be accelerated by 32. Test mode 1 is activated by setting bit 3, address 0, and causes all the time and date locations, address 2 to address9, to be incremented in parallel at 1 Hz with no carry over (independent of each other). The third test mode combines the previous two resulting in parallel incrementing at 32 Hz. |
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