Power, Reset, PLL Control, and Mode Selection

Power

The EM2000 should be powered from a stabilized DC power supply with a nominal output voltage of 3.3V (±5% tolerance). This power should be applied to pin #60. The "-A" modification of the EM2000 has a second VCC pin (#72). To prevent "current loops," use either pin (but not both pins) to supply power to the device.

The current consumption of the EM2000 is approximately 100mA (PLL on, 100BaseT mode). This does not include the power consumption of the wireless add-on module, such as the WA2000. This Wi-Fi add-on significantly increases the power consumed by the EM2000. Therefore, providing an adequate power supply is very important — a poorly built circuit may affect EM2000 operation. We recommend that you use a switching power supply.

For correct device operation, the VCCB line should not be left unconnected. You may connect this line to the backup battery or main 3.3V power (see Real-Time Counter).

Reset

A proper external reset is not required. The EM2000 has a reliable power-on reset circuit with brown-out detection. Optionally, you can connect a reset button or some other reset-generating circuit to the RST pin of the EM2000. This will allow you to generate external resets. The RST line has active LOW polarity. If you are not using the RST pin, you can leave it unconnected.

PLL Control

The EM2000 can run at three clock frequencies (speeds):

• Full speed: 120MHz (default post-reset speed)
• Medium speed: 43Mhz
• Low speed: 16MHz

The clock speed can be changed programmatically via the sys. object.

Mode Selection

The function of the MD line is described in Setup (MD) Button (Line).