参数资料
| 型号： | PIC12F635T-I/MF |
| 厂商： | Microchip Technology |
| 文件页数： | 13/74页 |
| 文件大小： | 0K |
| 描述： | IC MCU FLASH 1KX14 8DFN |
| 标准包装： | 3,300 |
| 系列： | PIC® 12F |
| 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，POR，WDT |
| 输入/输出数： | 5 |
| 程序存储器容量： | 1.75KB（1K x 14） |
| 程序存储器类型： | 闪存 |
| EEPROM 大小： | 128 x 8 |
| RAM 容量： | 64 x 8 |
| 电压 - 电源 (Vcc/Vdd)： | 2 V ~ 5.5 V |
| 振荡器型： | 内部 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 8-VDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 配用： | AC164324-ND - MODULE SKT FOR MPLAB 8DFN/16QFN XLT08DFN2-ND - SOCKET TRANSITION ICE 14DIP/8DFN AC162057-ND - MPLAB ICD 2 HEADER 14DIP XLT08DFN-ND - SOCKET TRANSITION ICE 8DFN AC164032-ND - ADAPTER PICSTART PLUS 8DFN/DIP AC124001-ND - MODULE SKT PROMATEII 8DIP/SOIC |
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Micrel, Inc.
KSZ8841-PMQL
October 2007
20
M9999-100407-1.5
LinkMD Cable Diagnostics
The KSZ8841-PMQL LinkMD uses time domain reflectometry (TDR) to analyze the cabling plant for common cabling
problems such as open circuits, short circuits, and impedance mismatches.
LinkMD works by sending a pulse of known amplitude and duration down the MDI and MDI-X pairs and then analyzes
the shape of the reflected signal. Timing the pulse duration gives an indication of the distance to the cabling fault with a
maximum distance of 200m and an accuracy of +/–2m.
Access
LinkMD is initiated by accessing register P1VCT, the LinkMD Control/Status register, in conjunction with register
P1CR4, the 100BASE-TX PHY Controller register.
Usage
LinkMD can be run at any time. To use LinkMD, disable HP Auto-MDIX by writing a ‘1’ to P1CR4[10] to enable manual
control over the pair used to transmit the LinkMD pulse. The self-clearing cable diagnostic test enable bit, P1VCT[15], is
set to ‘1’ to start the test on this pair.
When bit P1VCT[15] returns to ‘0’, the test is complete. The test result is returned in bits P1VCT[14-13] and the
distance is returned in bits P1VCT[8-0]. The cable diagnostic test results are as follows:
00 = Valid test, normal condition
01 = Valid test, open circuit in cable
10 = Valid test, short circuit in cable
11 = Invalid test, LinkMD failed
If P1VCT[14-13]=11 case, this indicates an invalid test, occurs when the KSZ8841-PMQL is unable to shut down the
link partner. In this instance, the test is not run, since it would be impossible for the KSZ8841-PMQL to determine if the
detected signal is a reflection of the signal generated or a signal from another source.
Cable distance (in meters) can approximately be determined by the following formula:
Distance = P1VCT[8-0] x 0.4m
This constant may be calibrated for different cabling conditions, including cables with a velocity of propagation that
varies significantly from the norm.
Media Access Control (MAC) and other
The KSZ8841-PMQL strictly abides by IEEE 802.3 standards to maximize compatibility.
Inter Packet Gap (IPG)
If a frame is successfully transmitted, the minimum 96-bits time for IPG is between the two consecutive packets. If the
current packet is experiencing collisions, the minimum 96-bits time for IPG is from carrier sense to the next transmit
packet.
Back-Off Algorithm
The KSZ8841-PMQL implements the IEEE standard 802.3 binary exponential back-off algorithm in half-duplex mode.
After 16 collisions, the packet is dropped.
Late Collision
If a transmit packet experiences collisions after 512 bit times of the transmission, the packet is dropped.
Flow Control
The KSZ8841-PMQL supports standard 802.3x flow control frames on both transmit and receive sides.
On the receive side, if the KSZ8841-PMQL receives a pause control frame, the KSZ8841-PMQL will not transmit the
next normal frame until the timer, specified in the pause control frame, expires. If another pause frame is received
before the current timer expires, the timer will be updated with the new value in the second pause frame. During this
period (while it is flow controlled), only flow control packets from the KSZ8841-PMQL are transmitted.
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