vt82885 ETC-unknow, vt82885 Datasheet
vt82885
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vt82885 Summary of contents
Page 1
... DESCRIPTION The VT82885 Real Time Clock is designed direct replacement for the DS12885. The VT82885 is identical in form, fit and function to the DS12885. It has 114 bytes of general purpose RAM. Access to this RAM space is determined by the logic level presented on AD6 during the address portion of an access cycle ...
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... Ground X1 32.768 kHz Crystal Connec- tions Volt Battery Input BAT RCLR# - RAM Clear tions of the VT82885. The following para- graphs describe the function of each pin. +8 PERIODIC INTERUPT SQUARE WAVE SELECTOR REGISTERS A,B,C,D CLOCK/ CLOCK, CALENDAR CALENDAR AND ALARM RAM UPDATE ...
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... VIA Technologies, Inc. power is applied. When V falls below 4.25 CC volts, the chip select input is internally forced to an inac-tive level regardless of the value of CS# at the input pin. The VT82885 is, therefore, write-protected. When V below the level the external V BAT supply is switched off and the external V lithium energy source supplies power to the Real Time Clock and the RAM memory ...
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... WR# (Write Strobe) to indicate a write cycle. CS# (Chip Select Input) signal must be asserted low for a bus cycle in the VT82885 to be accessed. CS# must be kept in the active state during RD# and WR#. Bus cycles which take place without asserting CS# will latch addresses but no access will occur. When V volts, the VT82885 internally inhibits access cycles by internally disabling the CS# input ...
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... J. Update Ended Interrupt Enable (UIE) is cleared to zero typical application RESET# can be connected This connection will allow CC the VT82885 and out of power fail without affecting any of the control registers. FIGURE 2: ADDRESS MAP VT82885 Bytes Clock and Control ...
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... The “don’t care” codes in all three alarm bytes create an interrupt every second. DECIMAL RANGE RANGE BINARY DATA MODE 0-59 00-3B 0-59 00-3B 0-59 00-3B 0-59 00-3B 1.12 01-0C AM, 81-8C PM 0-23 00-17 1-12 01-0C AM, 81-8C PM 0-23 00-17 1-7 01-07 1-31 01-1F 1-12 01-0C 0-99 00-63 NONVOLATILE RAM 6 VT82885 Real Time Clock BCD DATA MODE 00-59 00-59 00-59 00-59 01-12AM,81-92PM 00-23 01-12AM,81-92PM 00-23 01-07 01-31 01-12 00-99 ...
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... VIA Technologies, Inc. The 114 general purpose nonvolatile RAM bytes are not dedicated to any special func- tion within the VT82885. They can be used by the processor program as nonvolatile memory and are fully available during the update cycles. INTERRUPTS The RTC plus RAM includes three separate, fully automatic sources of interrupt for a pro- cessor ...
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... UPDATE CYCLE The VT82885 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 in- crements ...
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... AIE bit is set to zero, the AF bit does not iniate the IRQ# signal. The RE-SET# pin clears AIE to zero. The internal functions of the VT82885 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 VT82885 Real Time Clock LSB ...
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... I 5 CC1 -1.0 MOT I -1 4.0 4.25 TP MIN TYP OUT = 4.5V TO 5.5V) CC MIN TYP t 385 CYC PW 150 EL 11 VT82885 Real Time Clock MAX UNITS NOTES MAX UNITS NOTES +1 +1 +500 1,5 4 4.5 V MAX ...
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... IRDS t IRR t 244 BUC 1708 UC pin and the SQW pin when each is in the high impedence state. 4. The IRQ# pin is open drain. 5. Measured with a load as shown in Figure 4. 12 VT82885 Real Time Clock 120 ...
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... VIA Technologies, Inc. D.U.T. VT82885 BUS TIMING FOR WRITE CYCLE +5 VOLTS 1 680 13 VT82885 Real Time Clock ...
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... VIA Technologies, Inc ASD RD# t ASD WR# CS# AD0-AD7 VT82885 BUS TIMING FOR READ CYCLE t CYC PW ASH t ASED AHL t t ASL DSW 14 VT82885 Real Time Clock DHW ...
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... VIA Technologies, Inc ASD RD# t ASD WR# CS# AD0-AD7 VT82885 IRQ RELEASE DELAY TIMING RD# RESET# IRQ# POWER DOWN/POWER UP TIMING t CYC PW ASH t ASED DDR t AHL t ASL t RDS 15 VT82885 Real Time Clock DHR t RWL t IRR ...
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... PD t 300 F t 100 REC SYMBOL MIN TYP WARNING Under no circumstances are negative undershots, of any amplitude, allowed when device is in battery backup mode VT82885 Real Time Clock REC MAX UNITS NOTES 200 ms MAX UNITS NOTES years ...