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參數資料
| 型號： | MM58174 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Microprocessor-Compatible Real-Time Clock |
| 中文描述： | 微處理器兼容實時時鐘 |
| 文件頁數： | 4/8頁 |
| 文件大小： | 130K |
| 代理商： | MM58174 |
Circuit Description
(Continued)
TL/F/6681–3
FIGURE 2. Crystal Oscillator
DAYS COUNTER
There are two Days counters:
a) units of days
b) tens of days
The Days counters will count up to 28, 29, 30, or 31 days
depending on the state of the Months counters and the
Years Status Register. Days counters have parallel load and
read multiplex capabilities.
MONTHS COUNTERS
There are two Months counters:
a) units of months
b) tens of months
The Months counters have parallel load and read multiplex
capabilities.
YEARS STATUS REGISTER
The Years Status register is a shift register of 4 bits. It will be
shifted every year on December 31st. The status register
must be set in accordance with Table III. No readout capa-
bility is provided.
CHIP SELECT (CS)
An external chip select is provided. The chip enable is ac-
tive low.
COUNTER AND REGISTER SELECTION
Table I shows the coding on the address lines AD0–AD3
which select the registers in the circuit to be either parallel
loaded or read on to the output bus.
TL/F/6681–4
FIGURE 3. Test Mode Organization
START/STOP (RESET) LATCH
A logic ‘‘1’’ on DB0 at chip address 14 (E) will start the clock
running, a logic ‘‘0’’ will stop the clock. This function allows
the loading of time data into the clock and its precise start-
ing. The clock starts at 0.1 seconds.
TEST MODE
This mode is incorporated to facilitate production testing of
the circuit. In this mode, the 32,768 Hz clock is fed forward
as shown inFigure 3. For normal operation, the circuit must
be set to the non-test mode as part of the system initializa-
tion. This is accomplished by writing a logic ‘‘0’’ to DB3 at
AD0.
TABLE I. Address Decoding for Internal Registers
Selected
Counter
Address Bits
Mode
AD3 AD2 AD1 AD0
0 Test Only
1 Tenths of Secs.
2 Units of Secs.
3 Tens of Secs.
4 Units of Mins.
5 Tens of Mins.
6 Units of Hours
7 Tens of Hours
8 Units of Days
9 Tens of Days
10 Day of Week
11 Units of Months
12 Tens of Months
13 Years
14 Stop/Start
15 Interrupt
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Write Only
Read Only
Read Only
Read Only
Read or Write
Read or Write
Read or Write
Read or Write
Read or Write
Read or Write
Read or Write
Read or Write
Read or Write
Write Only
Write Only
Read or Write
4
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相關代理商/技術參數 |
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| MM58174AN | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Microprocessor-Compatible Real-Time Clock |
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