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参数资料
| 型号： | MM58274CN |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | XO, clock |
| 英文描述： | Microprocessor Compatible Real Time Clock |
| 中文描述： | 0 TIMER(S), REAL TIME CLOCK, PDIP16 |
| 封装： | 0.300 INCH, PLASTIC, DIP-16 |
| 文件页数： | 5/16页 |
| 文件大小： | 228K |
| 代理商： | MM58274CN |
Functional Description
The MM58274C is a bus oriented microprocessor real time
clock. It has the same pin-out as the MM58174A while offer-
ing extended timekeeping up to units and tens of years. To
enhance the device further, a number of other features have
been added including: 12 or 24 hours counting, a testable
data-changed flag giving easy error-free time reading and
simplified interrupt control.
A buffered oscillator signal appears on the interrupt output
when the device is in test mode. This allows for easy oscilla-
tor setting when the device is initially powered up in a sys-
tem.
The counters are arranged as 4-bit words and can be ran-
domly accessed for time reading and setting. The counters
output in BCD (binary coded decimal) 4-bit numbers. Any
register which has less than 4 bits (e.g., days of week uses
only 3 bits) will return a logic 0 on any unused bits. When
written to, the unused inputs will be ignored.
Writing a logic 1 to the clock start/stop control bit resets the
internal oscillator divider chain and the tenths of seconds
counter. Writing a logic 0 will start the clock timing from the
nearest second. The time then updates every 100 ms with
all counters changing synchronously. Time changing during
a read is detected by testing the data-changed bit of the
control register after completing a string of clock register
reads.
Interrupt delay times of 0.1s, 0.5s, 1s, 5s, 10s, 30s or 60s
can be selected with single or repeated interrupt outputs.
The open drain output is pulled low whenever the interrupt
timer times out and is cleared by reading the control regis-
ter.
CIRCUIT DESCRIPTION
The block diagram in Figure 1 shows the internal structure
of the chip. The 16-pin package outline is shown inFigure 2.
Crystal Oscillator
This consists of a CMOS inverter/amplifier with an on-chip
bias resistor. Externally a 20 pF capacitor, a 6 pF–36 pF
trimmer capacitor and a crystal are suggested to complete
the 32.768 kHz timekeeping oscillator circuit.
The 6 pF–36 pF trimmer fine tunes the crystal load imped-
ance, optimizing the oscillator stability. When properly ad-
justed (i.e., to the crystal frequency of 32.768 kHz), the cir-
cuit will display a frequency variation with voltage of less
than 3 ppm/V. When an external oscillator is used, connect
to oscillator input and float (no connection) the oscillator
output.
When the chip is enabled into test mode, the oscillator is
gated onto the interrupt output pin giving a buffered oscilla-
tor output that can be used to set the crystal frequency
when the device is installed in a system. For further informa-
tion see the section on Test Mode.
Divider Chain
The crystal oscillator is divided down in three stages to pro-
duce a 10 Hz frequency setting pulse. The first stage is a
non-integer divider which reduces the 32.768 kHz input to
30.720 kHz. This is further divided by a 9-stage binary ripple
counter giving an output frequency of 60 Hz. A 3-stage
Johnson counter divides this by six, generating a 10 Hz out-
put. The 10 Hz clock is gated with the 32.768 kHz crystal
frequency to provide clock setting pulses of 15.26
m
s dura-
tion. The setting pulse drives all the time registers on the
*
Use resistor with Ni-cad cells only
TL/F/11219–6
FIGURE 3. Typical System Connection Diagram
5
相关PDF资料 |
PDF描述 |
|---|---|
| MM58274CV | Microprocessor Compatible Real Time Clock |
| MM58341 | High Voltage Display Driver |
| MM58341N | High Voltage Display Driver |
| MM58341V | High Voltage Display Driver |
| MM58342 | MM58342 High Voltage Display Driver |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MM58274CN-12 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:MICROPROCESSOR COMPATIBLE REAL TIME CLOCK |
| MM58274CV | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Microprocessor Compatible Real Time Clock |
| MM58274CV-12 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:MICROPROCESSOR COMPATIBLE REAL TIME CLOCK |
| MM5829-2600RB8 | 制造商:MURATA-PS 制造商全称:Murata Power Solutions Inc. 功能描述:Coaxial Connectors (Chip Type Receptacle) |
| MM5829-2700RJ4 | 功能描述:RF 连接器 12GHz 0.035ohm JSC Type Connector RoHS:否 制造商:Bomar Interconnect 产品:Connectors 射频系列:BNC 型式:Jack (Female) 极性: 触点电镀:Gold 阻抗: 端接类型:Solder 主体类型:Straight Bulkhead 电缆类型: |
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