Epson RTC-72421 A - Manual (Page 4)

RTC - 72421 / 72423
Page - 1 MQ - 162 - 03
4-BIT PARALLEL INTERFACE REAL TIME CLOCK MODULE
RTC - 72421 / 72423
•
Built-in crystal unit removes need for adjustment and reduces installation costs
•
Microprocessor bus compatible ( tWW, t RD = 120 ns )
•
Use of C-MOS IC enables low current consumption ( 5
µ
A Max., at V DD = 2.0 V )
•
Compatibility with Intel CPU bus
•
Address latch enable (ALE) pin compatible with multiplex bus CPUs
•
Time (hours, minutes, seconds) and calendar (year, month, day) counter
•
24-hour/12-hour switchover and automatic leap-year correction functions
•
Fixed-period interrupt function
•
30-seconds correction (adjustment) function
•
Stop, start, and reset functions
•
Battery back-up function
•
Same mounting conditions as general-purpose SMD ICs possible (RTC-72423)
∗
Pins and functions compatible with the SMC-5242 series
„ Overview
The RTC-72421/RTC-72423 module is a real time clock that can be connected directly to a microprocessor's bus. Its built-in crystal
unit enables highly accurate time-keeping with no physical access required for adjustment and, since there is no need to connect
external components, mounting and other costs can be reduced.
In addition to its time and calendar functions, the RTC-72421/RTC-72423 enables the use of 30-seconds correction and fixed-
period interrupt functions.
The RTC-72421/RTC-72423 module is ideally suited for applications requiring timing management, such as personal computers,
dedicated word-processors, fax machines, multi-function telephones, and sequencers.
„ Block diagram
OSC
RESET
bit
STOP
bit
30sec ADJ
bit
Counter
HOLD
bit
BUSY
bit
D3
D2
D1
D0
WR
RD
A3
A2
A1
A0
CS0
ALE
CS1
S1 S10 MI1 MI10 H1 H10 W
D1 D10 MO1 MO10 Y1 Y10
64 Hz
1 Second carry
1 Minute carry
1 Hour carry
S1 to CF
CD CE CF
Gate
Gate
Latch Decoder
24/12
bit
RTC-72421/72423
STD.P
Output Selector