D/A (Modules F & J, Except J8)68C3 Operations Manual North Atlantic Industries, Inc. 12/19/2014Rev: 2014-12-19-0947 www.naii.com Page 130 of 330Words in FIFO:This is a counter that reports the number of data in a 2-byte word stored in the FIFO buffer. Every time a readoperation is made to the D/A FIFO Buffer Data memory address, its corresponding “Words in FIFO” counter willbe decremented by one. This register contains the number of data words in the buffer and is “dynamically”updated. In single shot mode (buffer control = 0x01), the software trigger pops out ‘size – 1’ words from the FIFO.Example: When Words in FIFO=10, and Size=11, initiating a trigger will read ten words from the FIFO resulting inWords in FIFO=0. The maximum number of words that can be stored in the FIFO is 26,213(0x6665).Description Words in FIFO (16-bit hex)Words in ch1-10 Data Range: (0x0000-0x6665)Hi-Threshold:The Hi-Threshold level is a value used to set the high limit bit (B2) of the individual channel status register inSystem memory location: 0x240 – 0x252. When the “Words in FIFO” counter is greater than or equal to the valuestored in the hi-threshold register, the high limit bit (B2) of the channel status register will be set. When the“Words in FIFO” counter is less than or equal to the value stored in the Lo-threshold register, the high limit bit (B2)of the channel status register will be reset (defaulted hysteresis).Set = “logical 1”Reset = “logical 0”Description Hi-Threshold (16-bit hex)Hi-Threshold in ch1-10 Data Range: (0x0000-0x6665)Lo-Threshold:The Lo-Threshold level is a value used to set or reset the low limit bit (B1) of the individual channel status registerin System memory location: 0x240 – 0x252. When the “Words in FIFO” counter is less than or equal to the valuestored in the Lo-Threshold, the low limit bit (B1) of the channel status register will be set. When the “Words inFIFO” counter is greater than or equal to the value stored in the Hi-Threshold, the low limit bit (B1) of the channelstatus register will be reset (defaulted hysteresis).Set = “logical 1”Reset = “logical 0”Description Low-Threshold (16-bit hex)Low-Threshold in ch1-10 Data Range: (0x0000-0x6665)Delay:Set the number of delay samples (based on the sample rate) before the actual FIFO data is “outputted” after atrigger is initiated. This sets a delay time after trigger prior to “outputting” the data.Description Delay (16-bit hex)Delay in ch1-10 Data Range: (0x0000-0xFFFF)Size:Sets the size of the FIFO buffer. The largest size that a FIFO buffer can be is 26,213(0x6665)Description Size (16-bit hex)Size in ch1-10 Data Range: (0x0000-0x6665)(If size is set to 0, the buffer will be read and output after triggering. The user must insure (via threshold orequivalent) that data is being “fed” to the buffer. Otherwise, if data in the buffer empties, the channel will outputthe last value. Note: It is recommended that Size be set as part of an initialization. It is not recommended tochange Size while there are words in the buffer.
