1,004
edits
Changes
Jump to navigation
Jump to search
mLine 69:
Line 69: − + + + + + Line 90:
Line 94: − +
no edit summary
| 0 || 0 || 0 || 0 || 0 || 0 || 0 || 0
| 0 || 0 || 0 || 0 || 0 || 0 || 0 || 0
|}
|}
Following this are 64 bytes of programming data listing the values for channels 0-31 (in that order) in 2-byte words. Each channel needs 14 bits, so the format is two leading zeros and 6 MSB of data is the first byte, then 8 LSB of data in the second byte. Place holders for all channels must be present in the packet, but only those marked in the mask will be programmed; all other bytes will be ignored and can take on any value. Regardless of the mask, the word corresponding to the ''last channel must be followed but another byte as padding.'' The packet format is shown in detail in the adjacent figure.
Following this are 64 bytes of programming data listing the values for channels 0-31 (in that order) in 2-byte words. Each channel needs 14 bits, so the format is two leading zeros and 6 MSB of data is the first byte, then 8 LSB of data in the second byte. The nominal transfer function of the DAC chip is:
<math>V=50*V_{ref}\frac{D}{2^{14}}</math>
where D is the 14-bit binary representation of the voltage value and <math>V_{ref}=3.3V</math> in the current board design, yielding a 0-165V range, assuming the recommended <math>10V+V_{max}=175V<math> power supply is used.
Place holders for all channels must be present in the packet, but only those marked in the mask will be programmed; all other bytes will be ignored and can take on any value. Regardless of the mask, the word corresponding to the ''last channel must be followed but another byte as padding.'' The packet format is shown in detail in the adjacent figure.
For real feedback, the "DAC health channel" may be used instead. The current control board hardware design specifies that DAC channel 31 be used as a DAC-health monitoring level. The line is connected with ADC channel 7. Assignment and reading back of values on this channel will be of great help in calibrating the DAC chip.
For real feedback, the "DAC health channel" may be used instead. The current control board hardware design specifies that DAC channel 31 be used as a DAC-health monitoring level. The line is connected with ADC channel 7. Assignment and reading back of values on this channel will be of great help in calibrating the DAC chip.
Channel ?? also has a special allocation: it controls the gain switch on the amplifier board.
Channel 18 also has a special allocation: it controls the gain switch on the amplifier board.