AMC6821 Register Setup

Boris ROUBINE

Other Parts Discussed in Thread: AMC6821

Hi,

I use the AMC6821.

I have an issue for the 1st readback of the tach speed. I read 0x0000. I expect 0xFFFF because the fan is stopped when I read the tach speed.

If I insert a tempo of around 2s, that becomes OK (ie I read 0xFFFF).

Why should I insert such a tempo ?

Hereunder, how I use the controller:

1- Power-ON

2- HW + SW init (more than 2s)

3- Init of AMC6821 as follows:

GENE_CONF_1 _X	0x00000091
GENE_CONF_2 _X	0x00000036
GENE_CONF_3 _X	0x00000082
GENE_CONF_4 _X	0x000000B8
FAN_DCY_REG_X	0x00000090
FAN_CHARACTERISTICS_X	0x0000001C

4- Read of TACH_DATA

Regards.

over 14 years ago

0 Rafael Ordonez over 14 years ago

TI__Expert 6925 points

Hello Boris,

It is important to be cautious with the START bit of “Conf. Reg. 1” because, at the moment is set to 1, the first monitoring cycle is started using settings currently present in the other registers. Any setting changed during this first monitoring cycle will not be applied until the next monitoring cycle.

If the Conf. Reg. 1 is written with value 0x91 before the others registers, then the first monitoring cycle has already started with default settings before your settings are written and applied. Therefore, your issue is that you are reading the default data (0x0000) of the TACH_DATA registers before the first monitoring cycle finishes and updates the TACH_DATA registers.

The main reason the first monitoring cycle takes such a long time is because it uses the default TACH-FAST bit of Conf. Reg. 4, which is zero. This forces the first monitoring cycle to last longer than a second.

My recommendation is to setup all other registers before the Configuration Register 1.

Regards,

0 Boris ROUBINE over 14 years ago in reply to Rafael Ordonez

Prodigy 20 points

Thank you so much Rafael.

I think that this is the root cause of my problem.

I'll check asap.

Regards.

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AMC6821 Register Setup