Datasheet

Propeller™ P8X32A Datasheet www.parallax.com

9.4. Typical Crystal Drive Current

This graph shows the current consumption of the crystal driver over a range of crystal frequencies and crystal settings, all

data points above 25 MHz were obtained by using a resonator since the driver does not perform 3

harmonic overtone

driving required for crystals over 25 MHz.

0 5 10 15 20 25 30 35 40 45 50

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Typical Crystal Drive Current (Vdd = 3.3 V, Ta = 25° C)

Current (mA)

xtal1

xtal2

xtal3

Frequency (MHz)

9.5. Cog and I/O Pin Relationship

The figure below illustrates the physical relationship between the cogs and I/O pins. While there can be a 1 to 1.5 ns

propagation delay in output transitions between the shortest and longest paths, the purpose of the figure is to illustrate the

length of leads and their associated parasitic capacitance. This capacitance increases the amount of energy required to

transition a pin’s state and therefore increases the current draw for toggling a pin. So, the current consumed by Cog 7

toggling P0 at 20 MHz will be greater than Cog 0 toggling P7 at 20 MHz. The amount of current consumed by transitioning a

pin’s state is dependent on many factors including: temperature, frequency of transitions, external load, and internal load. As

mentioned, the internal load is dependent upon which cog and pin are used. Internal load current for room temperature

toggling of a pin at 20 MHz for a Propeller in a DIP package varies on the order of 300 µA.

cog 0 cog 1 cog 2 cog 3 cog 4 cog 5 cog 6 cog 7

P10

P24

P23

P25

P26

P21

P22

P15

P16

P31