CDP1879 Intersil Corporation, CDP1879 Datasheet - Page 3

• Manufacturer Part Number: CDP1879
• Description: CMOS Real-Time Clock
• Manufacturer: Intersil Corporation

Bit 1, 0
Frequency 00
Bit 2
Start/Stop
Bit 3
Counter/Latch Control
“0” = Write to Counter and disable alarm
“1” = Write to and enable alarm Clock Select
Bit 7, 6, 5, 4
0000 - disable s
0001 - 488.2 s
0010 - 976.5 s
0011 - 1953.1 s
0100 - 3906.2 s
0101 - 7812.5 s
0110 - 15.625ms
0111 - 31.25ms
Select 01
CLOCK OUT
INT
RESET
V
V
A0
A1
A2
TPA
I-O MEM
TPB/WR
RD
CS
POWER DOWN
DD
SS
XTAL
XTAL
CONTROL REGISTER BIT ASSIGNMENT
DB0-DB7
10
11
OSCILLATOR
CLOCK AND
INTERFACE
INT. LOGIC
ADDRESS DECODE
CONTROL LOGIC
I/O
TABLE 1.
AND
INT. STATUS
REGISTER
PRESCALE
32768Hz
1.048576MHz
2.097152MHz
4.194304MHz
1 = Start
0 = Stop
1000 - 62.5ms
1001 - 125ms
1010 - 250ms
1011 - 500ms
1100 - sec.
1101 - min.
1110 - hour
1111 - day
PRESCALE
SELECT
FIGURE 1. REAL-TIME CLOCK FUNCTIONAL DIAGRAM
REGISTER
CONTROL
FREEZE
CIRCUIT
SELECT
CLOCK
CDP1879, CDP1879C-1
SECOND
4-106
SECOND
Latch, Counter Seconds
Latch, Counter Minutes
Latch, Counter Hours
Counter, Day
Counter, Month
Control, Register
Status Register
MSB of Hours Counters (Bit 7) is an AM-PM Bit. 0 = AM; 1 = PM
Bit 6 of Hours Counter Controls 12/24 hr. 1 = 12 Hr: 0 = 24 Hr.
Status Register: Bit 7 MSB = Alarm
Interrupt Source: Bit 6 = Clock.
MSB of Month Counter (Bit 7) is a Leap Year Bit 0 = No, 1 = Yes.
LATCH
MINUTE
ADDRESSES
8-BIT DATA BUS
COMPARATOR
MINUTE
LATCH
HOUR LOGIC
AM - PM
HOUR
AND
LATCH
TABLE 2.
HOUR
A2
0
0
1
1
1
1
1
CALENDAR
LOGIC
DAY
A1
1
1
0
0
1
1
1
MONTH
A0
0
1
0
1
0
1
1