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9-3. MC146818 (Real time clo'ck); .. ] ...
Advance Information·
.
;;:"
REAL·TIME CLOCKPLUSHAM
(RT~)
The
MC14681aReai~TimetJock
plus flAM Isa peripheraJdevice
which :inchjdes:'-the'
uniq'ue'MOTEL
conc'ePt for us-e with
various
microprocessors,-"
microcomputers~---and
larger
computers., This part
'combines three unique .features: a
complete
time-af-day
Clock
with
alarm and
one hundred
year
calender,
a programmable periodiC:' inter~
-~. [tip-Limd-sqlJaFe;-wav~~ieFlefat0IT-ana;-s(}:;byte~ci:pjow=poWerstatiC
;
RAM.T~e
MC146818 uses
high-~p~e(:1
CMOS technology to interface
:wi,th 1~ M,Hz _f?~c?~~so~)~u.~~s, whit~ consLHning}{~ryJittJEl power.
The
'Real-Ti~~-
cioek
pl~~
__
RAM'
tl~s
W;o 'distinct' uses. First, it is
'desig-ned as
ci'
'batterY- powelred:
CMOS
-'part~-(in'
an
otherwise
NMosmL system) inCluding all the common battery backed-up func!
tions,:such as RAM" time,-and calender.· Secondly, the MC146818
·mp.y be used.~itb a CMOS microproces,sor, f6,-reii~v~
the
software of
ther- timE!keeping·"\.vorkioad ahct
'to<:~xfent(the
aVfiilable RAM of an
iMPU such as the MC146805E2...
,. LOW-Power, High'Speed, High'DensityCMOS;·
' •. :Ihterrial Time· Base ahct··Osciliator
;. Counts Seconds, 'Minut:es"
aiid
Hours o(th-e bay
.
CoGn~s
Days of the Week; Oatei Month, and Year
3 V to 6 V Operation
• Time Sase Input· Options: 4.194304 MHz, 1.048576 MHz, or
32.768 kHz
lime Base Oscillator for Parallel Resonant Crystals
40 to 200 IlW Typical Operating Power at Low Frequency Time
Sase
• 4.0 to 20 mW Typical
Operati'n~f
Poyjer' at High Frequency Time
Base
Binary or BCD Representation ,of lime, Calendar, and Alarm
12- or 24·Hour Clock with AM and PM in 12·Hour Mode
~.
·'Ne·
OSC1
..
OSC2;
·ADO
AD1
AD2
AD3
AD4
AD5
AD6
AD7
VSS
.• PIN ASSIGNMENI .
Fig. 9-4
VDD
SQW
PS
CKOUT.
-CKFS
IRQ
DS
NC
RlW
AS
CE
'.
;
Pin numbers in parentheses represent equivalent Z suffix chip carrier
pins. Pins that have not been designated for the chip carrier are not
connected.
eSC1·
--01;;:::::=
a'"'
" 0 0 _
VSS_
c,
os
"W
AS
",
r
----~::====+=====~=====f~~~:C~UT
CKFS
sow
IRa
JR~~~
Clcck.Alarlll.
CaienderAAM
(10 Bytes)
• Daylight Savings TIme Option
Automatic End of Month Recognition
Automatic Leap Year Compensation
Microprocessor Bus Compatible
MOTEL Circuit for Bus Universality
Multiplexed Bus for Pin Efficiency
AOQ-A07
.;CY.
BinillY
Increment
Interfaced with Software as 64 RAM Locations
14 Bytes of Clock and Control Registers
• 50 Bytes of General Purpose RAM
Status Bit Indicates Data Integrity
Sus Compatible Interrupt Signals (IRQ)
Three Interrupts are Separately Software Maskable and Testable
Time·of-Day Alarm, Once-per·Second to Once-per.Day
Periodic Rates from 30.5 IlS to SOD ms
End-of-Clock Update Cycle
Programmable Square-Wave Output Signal
Clock Output May Be Used as Microprocessor Clock Input
At Time Base Frequency
+
1 or
+
4
24-Pin Dual-In-Line Package
Chip Carrier Also Available
AS
as
R/iN
Fig.9-5 Block diagram
.l<-----,[VHIGH
VlOW
-----+1
User RAM
(50 Byte;)
ADD
---------4:---~~--------_Jo------,h_----
-AD7
READ
NOTE VHIGH=VDD-20V VLQW=O.8V for VDD.,5.0V'!10%
Fig. 9-6
_ _________________________________________________ ~6~----------------~M~C~1~4~6~8~18~b~u~s~t~im~i~ngL_ ____________ ___
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