Sun Microsystems S16A manual Trim Registers, Input Gain High Byte Values, Trim Register Use

S16A User’s Guide			Registers
	Value (hex)	AIN_	Description
	08xx	X1	Unit gain.
	09xx	X2	Gain factor 2.
	0Axx	X5	Gain factor 5.
	0Cxx	X10_1	First gain factor 10. Uses the first-stage gain at maximum.
	10xx	X10_2	Second gain factor 10. Uses the second-stage 10 x gain.
			Recommended for higher bandwidth.
	11xx	X20	Gain factor 20.
	12xx	X50	Gain factor 50.
	14xx	X100	Gain factor 100. Uses both stages at maximum.

Table 14. Input Gain (High Byte) Values

Trim Registers

The Analog Input Module contains six Digital-to-Analog converters (DACs) that control various trim adjustments on the S16A. The analog input and output signals can be level-shifted, and the input signal gains can be fine-tuned with these DACs. These trim DACs are controlled by six 8-bit trim registers. These trim registers are set with the D command, described in Analog Input Module Control Protocol beginning on page 34.

As Analog Input Module registers, these registers are accessed via the UART registers.

Trim Register	Use
2	controls the output trim for analog I/O channel 0
3	controls the output trim for analog I/O channel 1
4	controls the input gain trim for analog I/O channel 0
5	controls the input offset for analog I/O channel 0
6	controls the input gain trim for analog I/O channel 1
7	controls the input offset for analog I/O channel 1

Table 15. Trim Registers

Trim Output Offset Registers

These two trim registers control a voltage offset for the output of each analog I/O channel. Trim register 2 controls the output trim for analog I/O channel 0; trim register 3 controls the output trim for channel 1.

The recommended procedure for adjusting these output trim registers is to first adjust one of the analog I/O channels’ input offset to be zero-calibrated by configuring its input to be ground and adjusting its input offset while monitoring the input data for zero. After setting up one of the analog I/O channels as a calibrated input, reconfigure the analog I/O channel input to monitor the analog I/O channel output in question. Finally, with all zeros for the output data, adjust the output trim until zeros are read in the input channel.

EDT, Inc. October, 1996 33