Motorola MPC505EVB Manual de usuario descargar pdf (Pagina 16)

HARDWARE PREPARATION AND INSTALLATION

2-6 MPC505EVBUM/D

2.2.2 Clock Source Select Header (J2)

Use jumper header J2 to select either a crystal or clock oscillator as the MCU clock source. The

drawing below shows the factory configuration: bus wire soldered on pins 2 and 3. This

configuration selects the crystal clock source; crystal in socket at located Y1. When you want to

use the clock oscillator as the EVB clock, move the bus wire on J2 from pins 2 and 3 to pins 1

and 2 and remove the bus wire on J1 (see paragraph 2.2.1). This disconnects the MCU XTAL pin

from the crystal clock circuit at location Y1 and selects the crystal oscillator (U7) as the MCU

clock source. The frequency of the crystal clock circuit is 4 MHz. The frequency of the crystal

oscillator circuit can be as fast as 40 MHz.

321

Bus Wire

2.2.3 Keep Alive Power 2 Select Header (J3)

Jumper header J3 provides power to the MCU-internal RAM module via the MCU VKAPWR2

pin. You may use either the on-board +3.3 Vdc (jumper on J3 pins 1 and 2) or connect an

external +3.3 Vdc power supply to J3 pins 2 and 3. An external +3.3 Vdc power supply on J3

pins 2 and 3 will maintain MCU-internal RAM data after EVB power is turned OFF. To attach

an external power supply to VKAPWR2: remove the jumper on J3 pins 1 and 2, and connect the

power supply ground to J3 pin 3 and +3.3 Vdc to pin 2.

CAUTION

Applying power to the EVB with J4 removed and no external

power supply attached to J4 will damage the MPC505 MCU.

Always keep a jumper or an external +3.3 Vdc power supply on J4

pins 1 and 2. If using an external power supply, apply VKAPWR1

before powering up the EVB.

1 2 ... 11 12 13 14 15 16 17 18 19 20 21 ... 57 58

Sin comentarios

Motorola MPC505EVB Manual de usuario Pagina 16