参数资料
| 型号： | KS8995MA |
| 厂商： | Micrel Inc |
| 文件页数： | 19/73页 |
| 文件大小： | 0K |
| 描述： | IC SWITCH 10/100 5PORT 128PQFP |
| 标准包装： | 66 |
| 系列： | * |
| 类型： | * |
| 应用： | * |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 128-BFQFP |
| 供应商设备封装： | 128-PQFP（14x20） |
| 包装： | 散装 |
| 配用： | 576-1017-ND - BOARD EVAL EXPERIMENT KS8995M |
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KS8995MA
Micrel, Inc.
M9999-051305
26
May 2005
Late Collision
If a transmit packet experiences collisions after 512-bit times of the transmission, the packet is dropped.
Illegal Frames
The KS8995MA discards frames of less than 64 bytes and can be programmed to accept frames up to 1536 bytes in Register
4. For special applications, the KS8995MA can also be programmed to accept frames up to 1916 bytes in Register 4. Since
the KS8995MA supports VLAN tags, the maximum size is adjusted when these tags are present.
Flow Control
The KS8995MA supports standard 802.3x flow control frames on both transmit and receive sides.
On the receive side, if the KS8995MA receives a pause control frame, the KS8995MA 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 given in the second pause frame. During this period of flow control, only flow
controlled packets from the KS8995MA are transmitted.
On the transmit side, the KS8995MA has intelligent and efficient ways to determine when to invoke flow control. The flow control
is based on availability of the system resources, including available buffers, available transmit queues, and available receive
queues.
The KS8995MA flow controls a port that has just received a packet if the destination port resource is busy. The KS8995MA
issues a flow control frame (XOFF), containing the maximum pause time defined in IEEE standard 802.3x. Once the resource
is freed up, the KS8995MA sends out the other flow control frame (XON) with zero pause time to turn off the flow control (turn
on transmission to the port). A hysteresis feature is also provided to prevent over-activation and deactivation of the flow control
mechanism.
The KS8995MA flow controls all ports if the receive queue becomes full.
Half-Duplex Back Pressure
The KS8995MA also provides a half-duplex back pressure option (note: this is not in IEEE 802.3 standards). The activation
and deactivation conditions are the same as the ones given for full-duplex mode. If back pressure is required, the KS8995MA
sends preambles to defer the other station's transmission (carrier sense deference). To avoid jabber and excessive deference
as defined in IEEE 802.3 standard, after a certain period of time, the KS8995MA discontinues carrier sense but raises it quickly
after it drops packets to inhibit other transmissions. This short silent time (no carrier sense) is to prevent other stations from
sending out packets and keeps other stations in a carrier sense deferred state. If the port has packets to send during a back
pressure situation, the carrier-sense-type back pressure is interrupted and those packets are transmitted instead. If there are
no more packets to send, carrier-sense-type back pressure becomes active again until switch resources are free. If a collision
occurs, the binary exponential backoff algorithm is skipped and carrier sense is generated immediately, reducing the chance
of further colliding and maintaining carrier sense to prevent reception of packets.
To ensure no packet loss in 10BASE-T or 100BASE-TX half-duplex modes, the user must enable the following:
Aggressive backoff (Register 3, bit 0)
No excessive collision drop (Register 4, bit 3)
Back pressure (Register 4, bit 5)
These bits are not set as the default because this is not the IEEE standard.
Broadcast Storm Protection
The KS8995MA has an intelligent option to protect the switch system from receiving too many broadcast packets. Broadcast
packets are normally forwarded to all ports except the source port and thus use too many switch resources (bandwidth and
available space in transmit queues). The KS8995MA has the option to include “multicast packets” for storm control. The
broadcast storm rate parameters are programmed globally and can be enabled or disabled on a per port basis. The rate is based
on a 50ms interval for 100BT and a 500ms interval for 10BT. At the beginning of each interval, the counter is cleared to zero
and the rate limit mechanism starts to count the number of bytes during the interval. The rate definition is described in Registers
6 and 7. The default setting for Registers 6 and 7 is 0x4A (74 decimal). This is equal to a rate of 1%, calculated as follows:
148,800 frames/sec 50ms/interval 1% = 74 frames/interval (approx.) = 0x4A
MII Interface Operation
The media independent interface (MII) is specified by the IEEE 802.3 committee and provides a common interface between
physical layer and MAC layer devices. The KS8995MA provides two such interfaces. The MII-P5 interface is used to connect
to the fifth PHY, whereas the MII-SW interface is used to connect to the fifth MAC. Each of these MII interfaces contains two
distinct groups of signals, one for transmission and the other for receiving. Table 1 describes the signals used in the MII-P5
interface.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| KS8995MA_11 | 制造商:MICREL 制造商全称:Micrel Semiconductor 功能描述:Integrated 5-Port 10/100 Managed Switch |
| KS8995MA-EVAL | 功能描述:BOARD EVAL EXPERIMENT KS8995MA RoHS:否 类别:编程器，开发系统 >> 过时/停产零件编号 系列:- 标准包装:1 系列:- 类型:MCU 适用于相关产品:Freescale MC68HC908LJ/LK（80-QFP ZIF 插口） 所含物品:面板、缆线、软件、数据表和用户手册 其它名称:520-1035 |
| KS8995MAI | 功能描述:IC SWITCH 10/100 5PORT 128PQFP RoHS:否 类别:集成电路 (IC) >> 专用 IC 系列:* 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- 类型:调帧器 应用:数据传输 安装类型:表面贴装 封装/外壳:400-BBGA 供应商设备封装:400-PBGA（27x27） 包装:散装 |
| KS8995MAL | 功能描述:IC SWITCH 10/100 5PORT 128PQFP RoHS:否 类别:集成电路 (IC) >> 专用 IC 系列:* 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- 类型:调帧器 应用:数据传输 安装类型:表面贴装 封装/外壳:400-BBGA 供应商设备封装:400-PBGA（27x27） 包装:散装 |
| KS8995M-EVAL | 功能描述:BOARD EVAL EXPERIMENT KS8995M RoHS:否 类别:编程器，开发系统 >> 评估演示板和套件 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:- 主要目的:电源管理，电池充电器 嵌入式:否 已用 IC / 零件:MAX8903A 主要属性:1 芯锂离子电池 次要属性:状态 LED 已供物品:板 |
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