VT82887 ETC-unknow, VT82887 Datasheet
VT82887
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VT82887 Summary of contents
Page 1
... Periodic rates from 122 s to 500 ms - End of clock update cycle DESCRIPTION The VT82887 Real Time Clock is designed direct replacement for the DS12887. The VT82887 is identical in form, fit and function to the DS12887. It has 114 bytes of general purpose RAM. Access to this RAM space is ...
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... When V falls below 4.25 volts, the chip CC select input is internally forced to an inactive level regardless of the value of CS# at the input pin. The VT82887 is, therefore, write- remain protected. When V 8 PERIODIC INTERUPT SQUARE WAVE SELECTOR REGISTERS A,B,C,D ...
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... Address/data multiplexing does not slow the access time of 3 VT82887 Real Time Clock is less than 4.25 volts CC is not applied. The RCLR# ...
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... J. Update Ended Interrupt Enable (UIE) is The cleared to zero typical application RESET# can be connected to V the VT82887 and out of power fail without affecting any of the control registers. ADDRESS MAP The address map of the VT82887 is shown in Figure 2. The address map consists of 114 ...
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... All 128 bytes can be directly written or read except for the following: 1. Registers C and D are read-only. FIGURE 2: ADDRESS MAP VT82887 TIME, CALENDAR AND ALARM LOCATIONS The time and calendar information is obtained by reading the appropriate memory bytes. ...
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... Year NONVOLATILE RAM The 114 general purpose nonvolatile RAM bytes are not dedicated to any special function within the VT82887. They can be used by the processor program as nonvolatile memory and are fully available during the update cycle. INTERRUPTS at the specified time each day if the alarm enable bit is high. The second use condition is to insert a “ ...
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... C. A logic one in bit 7 (IRQF bit) indicates that Real Time Clock one or more interrupts have been initiated by the VT82887. The act of reading Register C clears all active flag bits and the IRQF bit. OSCILLATOR CONTROL BITS The VT82887’s internal oscillator can be turned on and off as required ...
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... VIA Technologies, Inc. The VT82887 executes an update cycle once per second regardless of the SET bit in Register B. When the SET bit in Register B is set to one, the user copy of the double buffered time, calendar and alarm bytes is frozen and will not update as the time increments ...
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... AIE bit is set to zero, the AF bit does not initiate the IRQ# signal. The RESET# pin clears AIE to zero. The internal functions of the VT82887 do not affect the AIE bit. UIE The Update Ended Interrupt Enable (UIE) bit is a read/write that enables the Update End Flag (UF) bit in Register C to assert IRQ# ...
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... RTC data and RAM data are questionable. This bit is unaffected by RESET#. BIT 6 THROUGH BIT 0 The remaining bits of Register D are not usable. They cannot be written and, when read, they will always read zero. 10 VT82887 Real Time Clock LSB ...
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... -1.0 MOT I -1 4.0 4.25 TP MIN TYP OUT = 4.5V TO 5.5V) CC MIN TYP t 385 CYC 150 EL 125 VT82887 Real Time Clock MAX UNITS NOTES MAX UNITS NOTES +1 +1 +500 1,5 4 4.5 V MAX ...
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... AHL t 25 ASD 60 ASH t 40 ASED t 20 DDR t 100 DSW t 5 RWL t IRDS t IRR t 244 BUC 1708 UC 5. Measured with a load as shown in Figure 4. 12 VT82887 Real Time Clock 120 See Table 1 s ...
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... VIA Technologies, Inc. D.U.T. VT82887 BUS TIMING FOR WRITE CYCLE +5 VOLTS 1 680 13 VT82887 Real Time Clock ...
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... VIA Technologies, Inc ASD RD# t ASD WR# CS# AD0-AD7 VT82887 BUS TIMING FOR READ CYCLE t CYC PW ASH t ASED AHL t t ASL DSW 14 VT82887 Real Time Clock DHW ...
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... VIA Technologies, Inc ASD RD# t ASD WR# CS# AD0-AD7 VT82887 IRQ RELEASE DELAY TIMING t CYC PW ASH t ASED DDR t AHL t ASL 15 VT82887 Real Time Clock DHR ...
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... VIA Technologies, Inc. RD# RESET# IRQ# POWER DOWN/POWER UP TIMING V CC 4.5V 3. CS# CURRENT SUPPLIED FROM EXTERNAL LITHIUM ENERGY CELL POWER DOWN/POWER UP TIMING t RDS DATA RETENTION VT82887 Real Time Clock t RWL t IRR REC ...
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... Under no circumstances are negative undershoots, of any amplitude, allowed when device is in battery backup mode. SYMBOL MIN TYP 300 F t 100 REC SYMBOL MIN TYP VT82887 Real Time Clock MAX UNITS NOTES 200 ms MAX UNITS NOTES years ...