User Manual

CDriver User Guide 26

7.5 Pull-up resistors

CDriver has 6 programmable pull-up resistors, 3 each for SDA and SCL. 6

control bits each enable or disable a pull-up resistor. These bits are:

bit resistor

0 2.2K to SDA

1 4.3K to SDA

2 4.7K to SDA

3 2.2K to SCL

4 4.3K to SCL

5 4.7K to SCL

At boot the two 4.7K resistors are enabled. By setting combinations of parallel

resistors, a range of pull-up strengths can be achieved:

4.7K 4.3K 2.2K pull-up strength

0 0 0 0 (i.e. no pull-up)

0 0 1 2.2K

0 1 0 4.3K

0 1 1 1.5K

1 0 0 4.7K

1 0 1 1.5K

1 1 0 2.2K

1 1 1 1.1K

Ordering this by useful resistances, the 3-bit combinations are:

3-bit value Resistance

0 0

1 2.2K

2 4.3K

4 4.7K

5 1.5K

7 1.1K