100BaseTX sending
The 100BaseTX transmission function performs parallel-to-serial conversion, 4B/5B encoding, scrambling code, NRZ to NRZI conversion,
MLT3 encoding and transmission. The circuit begins with serial conversion in parallel, which will come from the MII of the data
The MAC into a 125MHz serial bit stream. The data and control flow are then converted into 4B/5B encoded by scrambling.
The serialized data is further converted from NRZ to NRZI format and then transmitted at MLT3 current output. output
The current is externally 1% 3.01kΩ 1:1 transformer specific resistance. It has a typical rise/fall time and conforms to 4ns
Standard-related ANSI TP-PMD amplitude balance, overshoot, and timing jitter. Wavy 10BaseT output
A 100BaseTX transmitter is also included.
100BaseTX reception
Receive functions perform 100BaseTX adaptive equalization, DC recovery, MLT3 to NRZI conversion, data, and clocking
Recovery, NRZI to NRZ conversion, de-scramble, 4B/5B decoding and serial to parallel conversion. The receiving end starts
Filter with equalization of inter-symbol interference (ISI) compensation in twisted pair cables. Due to amplitude
Loss and phase distortion are feature on cable length, and the equalizer adjusts to optimize its characteristics
Performance. In this design, the variable equalizer makes a preliminary estimate based on the comparison of the input signal
For some known strength cable characteristics then its tune itself is optimized. It's an ongoing process and can
Self-adjusting such as temperature changes to environmental changes.
The equalization signal of goes is then restored through the DC and the data conversion block. This DC recovery circuit is used for:
Compensate for the effects of baseline drift and improve dynamic range. Differential data conversion circuit conversion
The MLT3 format goes back to NRZI. The slicing threshold is also adaptable.
The clock recovery circuit extracts the 125MHz clock from the edges of the NRZI signal. This recovered clock is then used to
The format is converted to NRZI NRZ signals. Send a signal and then scramble by canceling it by the 4B/5B decoder.
Finally, the NRZ serial data is converted to MII format and input data is provided to the MAC.
PLL clock synthesizer
The KS8997 generates system timing 125MHz, 62MHz, 25MHz and 10MHz clocks. The internal clock generates one
External 25MHz crystal.
Scrambling/descrambling (100BaseTX only)
The purpose of this scrambling code is to propagate the power spectrum of the signal to reduce EMI and baseline drift. should
The data is shifted through a wide linear feedback 11-bit register (LFSR).
Repeat sequences. The receiver will go to compete for the same order of input data streams that are transmitted.
10BaseT sends
Output 10BaseT drives are incorporated into 100BaseT drives allowing the same magnetic transmission. They are
Domestic wavy and pre-emptly for output emphasize a typical 2.3V amplitude.
10BaseT receives
At the receiving end, input buffering and level detection squelch circuits are employed. Differential input circuitry and a receiver
PLL performs decoding functions. Manchester-encoded data streams are split into clock signals and NRZ data. One
Squelch circuits reject less than 400mV or short pulse widths to horizontal signals to prevent noise at RXP or noise
RXM throws false trigger decoder. When the input exceeds the squelch limit, the PLL locks onto the input signal
and KS8997 to decode data frames. The idle time between receiver clock remains active and data is received.
power management
Power saving mode
The KS8997 will shut down everything except the energy detection circuit and PLL when the cable is not installed on the individual
Port Foundation. In other words the KS8997 will shut down most of the internal circuitry to save power if there is no contact.
MDI/MDI-X automatic crossover
The KS8997 supports MDI/MDI-X automatic crossover. This is beneficial either by connecting a cable directly or using the CAT-5
Crossover CAT-5 cable. Auto-sensing detects remote send and receive pairs and correctly distributes transmissions
and receive a pair of devices from McRell . This can be very useful when the end user does not know the type of cable that is okay
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