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| 型号： | PIC16F639T-I/SS |
| 厂商： | Microchip Technology |
| 文件页数： | 14/74页 |
| 文件大小： | 0K |
| 描述： | IC MCU FLASH 2KX14 20SSOP |
| 产品培训模块： | Asynchronous Stimulus |
| 标准包装： | 1,600 |
| 系列： | PIC® 16F |
| 核心处理器： | PIC |
| 芯体尺寸： | 8-位 |
| 速度： | 20MHz |
| 外围设备： | 欠压检测/复位，LVD，POR，WDT |
| 输入/输出数： | 11 |
| 程序存储器容量： | 3.5KB（2K x 14） |
| 程序存储器类型： | 闪存 |
| RAM 容量： | 128 x 8 |
| 电压 - 电源 (Vcc/Vdd)： | 2 V ~ 3.6 V |
| 振荡器型： | 内部 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 20-SSOP（0.209"，5.30mm 宽） |
| 包装： | 带卷 (TR) |
| 配用： | XLT20SS1-1-ND - SOCKET TRANSITION 20DIP 20SSOP AC162066-ND - HEADER INTRFC MPLAB ICD2 20PIN |
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Micrel, Inc.
KSZ8841-PMQL
October 2007
21
M9999-100407-1.5
On the transmit side, the KSZ8841-PMQL has intelligent and efficient ways to determine when to invoke flow control.
The flow control is based on availability of the system resources.
The KSZ8841-PMQL issues a flow control frame (XON), containing the maximum pause time defined in IEEE standard
802.3x. Once the resource is freed up, the KSZ8841-PMQL sends out another flow control frame (XOFF) with zero
pause time to turn off the flow control (turn on transmission to the port). A hysteresis feature is provided to prevent the
flow control mechanism from being constantly activated and deactivated.
Half-Duplex Backpressure
A half-duplex backpressure option (non-IEEE 802.3 standards) is also provided. The activation and deactivation
conditions are the same as above in full-duplex mode. If backpressure is required, the KSZ8841-PMQL sends
preambles to defer the other stations' transmission (carrier sense deference).
To avoid jabber and excessive deference (as defined in the 802.3 standard), after a certain time, the KSZ8841-PMQL
discontinues the carrier sense and then raises it again quickly. This short silent time (no carrier sense) prevents other
stations from sending out packets thus keeping other stations in a carrier sense deferred state. If the port has packets
to send during a backpressure situation, the carrier sense type backpressure is interrupted and those packets are
transmitted instead. If there are no additional packets to send, carrier sense type backpressure is reactivated again until
chip resources free up. If a collision occurs, the binary exponential back-off algorithm is skipped and carrier sense is
generated immediately, thus reducing the chance of further colliding and maintaining carrier sense to prevent packet
reception.
The backpressure will take effect automatically in Auto-negotiation enable and half-duplex mode.
Clock Generator
The X1 and X2 pins are connected to a 25MHz crystal. X1 can also serve as the connector to the 3.3V 25MHz oscillator
(as described in the pin description).
EEPROM Interface
An external serial EEPROM with a standard microwire bus interface is used for non-volatile storage of information such
as the node address and subsystem ID.
As part of the initialization after system reset, the KSZ8841-PMQL reads the external EEPROM and places the data
into certain host-accessible registers if the EEEN pin is pulled-up, the KSZ8841-PMQL performs an automatic read of
the EEPROM word from 0x0 to 0x6 after the de-assertion of Reset. An EEPROM of 1KB(93C46) or 4KB(93C66) can be
used based on application.
The EEPROM read/write function can also be performed by software reading and writing to the EEPCR register.
The KSZ8841-PMQL EEPROM format is given in Table 2.
WORD
15
8
7
0
0x0
Reserved
0x1
MAC Address Byte 2
MAC Address Byte 1
0x2
MAC Address Byte 4
MAC Address Byte 3
0x3
MAC Address Byte 6
MAC Address Byte 5
0x4
0x5
0x6
0x7-0x3F
Subsystem ID
Subsystem Vendor ID
ConfigParam
Not used by KSZ8841-PMQL (available for user to use)
Table 2. KSZ8841-PMQL EEPROM Format
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| PIC16F648A-E/ML | 功能描述:8位微控制器 -MCU 7KB 256 RAM 16 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT |
| PIC16F648A-E/P | 功能描述:8位微控制器 -MCU 7KB 256 RAM 16 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT |
| PIC16F648A-E/SO | 功能描述:8位微控制器 -MCU 7KB 256 RAM 16 I/O RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT |
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