1. Crystal oscillator, whether it is the Mii 25M, or rmii 50M, the output must be 50ppm, for DM9161AEP, the best XT1, for DM9161CEP, XT1,XT2 can be.
2.pin31-ledmode, this direct connection 3.3V, do not need to add resistance, otherwise the speed light is darker. This 31 feet, if grounded, speed does not blink.
3.pin39-auto-mdix Direct grounding.
4.pin47-48 6.8K resistance, must be 1% precision, and to be connected to the AGND
5.pin1,2,9 output level, measured. A 0.1uf filter capacitor, a 220uf voltage regulator, is required here. The voltage here is supplied to the network transformer.
6. Network transformer rx﹢-,tx﹢-, 49.9 resistance, must be 1% accuracy, otherwise easy to lose packets
7.PCB Cloth Board, the chip and the network transformer part of the distance not more than 2cm, otherwise easy to drop packets, differential line as far as possible equivalence
8.RJ45 socket cannot be reversed, otherwise it cannot be ping
Reference: http://www.wangchao.net.cn/bbsdetail_1764954.html
