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| 型号： | SX28AC/SSU |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | 2 CHANNEL(S), I2C BUS CONTROLLER, PDSO28 |
| 封装： | GREEN, PLASTIC, SSOP-28 |
| 文件页数： | 17/48页 |
| 文件大小： | 772K |
| 代理商： | SX28AC/SSU |
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2005 Ubicom, Inc. All rights reserved.
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SX20AC/SX28AC
10.2 Watchdog Timer
The watchdog logic consists of a Watchdog Timer which
shares the same 8-bit programmable prescaler with the
RTCC. The prescaler actually serves as a postscaler if
used in conjunction with the WDT, in contrast to its use as
a prescaler with the RTCC. The WDT is clocked by it’s
own internal RC oscillator.
The Watchdog oscillator has a nominal operating fre-
quency of 16 kHz, or a period of 62.5 microseconds. At
this rate, the 8-bit counter counts from 00h to FFh in 16
milliseconds. In the default configuration (prescaler
assigned to WDT, with divide rate set to 1:128), the appli-
cation program needs to execute a “CLR !WDT” instruc-
tion at least once every 2 seconds to prevent a Watchdog
reset (if the WDTE bit in the FUSE register is set to 1).
See Table 4-2.
10.3 The Prescaler
The 8-bit prescaler may be assigned to either the RTCC
or the WDT through the PSA bit (bit 3 of the OPTION reg-
ister). Setting the PSA bit assigns the prescaler to the
WDT. If assigned to the WDT, the WDT clocks the pres-
caler and the prescaler divide rate is selected by the
PS0, PS1, and PS2 bits located in the OPTION register.
Clearing the PSA bit assigns the prescaler to the RTCC.
Once assigned to the RTCC, the prescaler clocks the
RTCC and the divide rate is selected by the PS0, PS1,
and PS2 bits in the OPTION register. The prescaler is not
mapped into the data memory, so run-time access is not
possible.
The prescaler cannot be assigned to both the RTCC and
WDT simultaneously.
Figure 10-1. RTCC and WDT Block Diagram
WDTE (from FUSE Word)
RTCC pin
MUX
8-Bit Prescaler
MUX (8 to 1)
8-Bits
WDT Time-out
Data Bus
WDT
MUX
M
RTCC
M
U
X
FOSC
RST
RTE_ES
PSA
PS2
PS1
PS0
OPTION
Register
RTCC Rollover
Interrupt
RTE_IE
RTW
RTCC
Interrupt
Enable
U
X
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SX28AD100-I/DP | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Configurable Communications Controllers with EE/Flash Program Memory, In-System Programming Capability and On-Chip Debug |
| SX28AD100-I/PQ | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Configurable Communications Controllers with EE/Flash Program Memory, In-System Programming Capability and On-Chip Debug |
| SX28AD100-I/SO | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Configurable Communications Controllers with EE/Flash Program Memory, In-System Programming Capability and On-Chip Debug |
| SX28AD100-I/SS | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Configurable Communications Controllers with EE/Flash Program Memory, In-System Programming Capability and On-Chip Debug |
| SX28AD100-I/TQ | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Configurable Communications Controllers with EE/Flash Program Memory, In-System Programming Capability and On-Chip Debug |
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