VT82885N ETC-unknow, VT82885N Datasheet

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VT82885N

Manufacturer Part Number
VT82885N
Description
Manufacturer
ETC-unknow
Datasheet
FEATURES
DESCRIPTION
The VT82885 Real Time Clock is designed
to be a 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. An external
crystal and battery are the only components
required to maintain time-of-day and
memory status in the absence of power. A
complete description of operating conditions,
Drop-in replacement for IBM AT computer
clock/calendar.
Pin configuration closely matches the
DS12887, DS12885and DS12885Q
Counts seconds, minutes, hours, days,
day of the week, date, month, and year
with leap year compensation
Binary or BCD representation of time,
calendar and alarm
12- or 24-hour clock with AM and PM in
12-hour mode
Daylight Savings Time option
Intel bus timing
Multiplex bus for pin efficiency
Interfaced with software as 128 RAM
locations
- 14 bytes of clock and control registers
- 114 bytes of general purpose RAM
Programmable square wave output signal
Bus-compatible interrupt signals (IRQ#)
Three interrpts are separately software-
maskable and testable
- Times-of-day alarm once/second to
- Periodic rates from 122 s to 500 ms
- End of clock update cycle
Optional 28-pin PLCC surface mount
package
once/day
VIA Technologies, Inc.
1
electrical characteristics, bus timing and pin
descriptions follows.
PIN ASSIGNMENT
GND
GND
AD0
AD1
AD2
AD3
AD4
AD5
PIN DESCRIPTION
AD0-AD7
NC
CS#
AS
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
11
NC
5
4
X1
X2
X
2
6
7
8
9
10
A
D
6
1
2
3
4
5
6
7
8
9
10
11
12
VT82885 28-PIN PLCC
X
1
3
13 14 15 16 17
N
C
VT82885 24 PIN DIP
- Multiplexed Address/Data Bus
- No Connection
- Chip Select
- Address Strobe
G
N
D
2
A
D
7
N
C
1
G
N
D
Real Time Clock
V
CC
28
C
S
#
S
Q
W
27
A
S
24
23
22
21
20
19
18
17
16
15
14
13
24
23
22
21
20
N
C
N
C
VT82885
V
SQW
NC
RCLR#
V
IRQ#
RESET#
RD#
NC
WR#
AS
CS#
RCLR#
V
IRQ#
RESET#
RD#
GND
WR#
26
25
19
18
CC
BAT
BAT

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VT82885N Summary of contents

Page 1

VIA Technologies, Inc. FEATURES Drop-in replacement for IBM AT computer clock/calendar. Pin configuration closely matches the DS12887, DS12885and DS12885Q Counts seconds, minutes, hours, days, day of the week, date, month, and year with leap year compensation Binary or BCD representation ...

Page 2

VIA Technologies, Inc. WR# - Write Strobe RD# - Read Strobe RESET# - Reset Input IRQ# - Interrupt Request Output SQW - Square Wave Output Volt Supply CC OPERATION The block diagram in Figure 1 shows the ...

Page 3

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 ...

Page 4

VIA Technologies, Inc. X1, X2 These pins connect to a standard 32.768 kHz quartz crystal. The internal os- cillator circuitry is designed for operation with a crystal having a specified load capa- citance (CL pF. Each of the ...

Page 5

VIA Technologies, Inc. E. Periodic Interrupt Flag (PF) bit is cleared to zero. F. The device is not accessible until RESET# is returned high. G. Alarm Interrupt Flag (AF) bit is cleared to zero. H. IRQ# pin is in the ...

Page 6

VIA Technologies, Inc. should be written to a logic one to prevent updates from occurring while access is be- ing attempted. In addition to writing the ten time, calendar and alarm registers in a se- lected format (binary or BCD), ...

Page 7

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. ...

Page 8

VIA Technologies, Inc. lected using the same Register A bits which selected the square wave frequency (see Table 1). Changing the Register A bits af- fects both the square wave frequency and the periodic interrupt output. However, each function has ...

Page 9

VIA Technologies, Inc. MSB BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 UIP DV2 DV1 DV0 RS3 RS2 UIP The Update in Progress (UIP) bit is a status flag that can be ...

Page 10

VIA Technologies, Inc. by the RESET# pin. SQWE is a read/write bit. DM The Data Mode (DM) bit indicates whether time and calendar information is in binary or BCD format. The DM bit is set by the program to the ...

Page 11

VIA Technologies, Inc. VOLTAGE ON ANY PIN RELATIVE TO GROUND -0.3V TO +7.0V OPERATING TEMPERATURE STORAGE TEMPERATURE SOLDERING TEMPERATURE *This is a stress rating only and functional operation of the device at these or any other conditions above those indicated ...

Page 12

VIA Technologies, Inc. Pulse Width, DS/E High or PW RD/WR# Low Input Rise and Fall Time R/W# Hold Time R/W# Setup Time before DS/E Chip Select Setup Time before DS, WR#, or RD# Chip Select Hold Time Read Data Hold ...

Page 13

VIA Technologies, Inc. D.U.T. VT82885 BUS TIMING FOR WRITE CYCLE +5 VOLTS 1 680 13 VT82885 Real Time Clock ...

Page 14

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 ...

Page 15

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 ...

Page 16

VIA Technologies, Inc 4.5V V BAT CS# CURRENT SUPPLIED FROM EXTERNAL LITHIUM ENERGY CELL POWER DOWN/POWER UP TIMING PARAMETER CS before Power-Down IH V slew from 4. (CS# at ...

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