DESCRIPTION

The National Instruments X series data acquisition boards have four 32-bit counter channels and 8 or 32 digital I/O (DIO) channels (depending on model). Different models include a varying number of analog-to-digital converters (ADC) and digital-to-analog converters (DAC). However, the ADC and DAC functionality is not yet supported by spec.

Recognized models are PCIe-6320, PCIe-6321, PCIe-6323, PCIe-6341, PCIe-6343, PCIe-6351, PCIe-6353, PCIe-6361 and PCIe-6363, along with PXIe-6323, PXIe-6341, PXIe-6343, PXIe-6356, PXIe-6358, PXIe-6361, PXIe-6366, PXIe-6368, PXIe-6376 and PXIe-6378.

All models support a 100 MHz count rate. In addition, counter inputs may be prescaled by a factor of two or eight extending the usable maximum count rates to 200 MHz or 800 MHz, and adding one or three more bits to the effective counter size.

When counting to time, for shorter count times (less than 42.95 seconds), spec uses the 100 MHz built-in clock. For longer count times, spec uses the 100 KHz clock, allowing for a maximum count time of nearly 12 hours.

spec will keep track of overflows to the channel counting time (when not counting to a time preset), but does not currently correct for counter overflows in the other channels.

spec also provides commands for selecting the hardware's digital debouncing filter for external inputs and for accessing the DIO pins available on these cards. See the FUNCTIONS section below for details.

SOFTWARE CONFIGURATION

Use spec's configuration editor (edconf, normally invoked by the config macro) to select the timer and to configure the scaler channels. On the Devices screen, enter the the number of counters on the board, which should be four.

SCALERS  DEV  ADDR  <>MODE  NUM                          <>TYPE
    YES        0:0            4    NI PCI 63xx as Counter/Timer
    YES        0:0            4         NI PCI 63xx as Counters

The ADDR field can be optionally used to configure the PCI bus:slot numbers if more than one of these cards is installed in the same computer. Leaving the default value of 0:0 means the card can be in any slot. Note, the values must be entered as decimal numbers in spec's configuration editor, even though the Linux /sbin/lspci utility will list the values in hexadecimal. For cards with ADDR set to the default 0:0, spec will assign unit numbers in the order in which the cards are detected.

The parameters "active_low" and "io_config" can be set as optional controller parameters by typing the p command. Enter the parameter name and value on the optional parameter screen. Possible values are described in the FUNCTIONS section below. When set only as a controller parameter, the parameter value cannot be changed from the spec command line.

On the Scaler screen, choose NI63xx as the device type. The unit numbers are assigned consecutively to the NI PCI counter/timers according to the order they are listed on the Devices screen, starting with unit zero:

NUMBER      NAME  MNEMONIC  <>DEVICE  UNIT  CHAN   <>USE AS  SCALE
     0   Seconds       sec    NI63xx     0     0   timebase      1
     1   Monitor       mon    NI63xx     0     1    monitor      1
     2  Detector       det    NI63xx     0     2    counter      1
     3 Counter 2        c2    NI63xx     0     3    counter      1
     3 Counter 3        c3    NI63xx     1     0    counter      1
     3 Counter 4        c4    NI63xx     1     1    counter      1

Any channel can be used as the time base. Also, any channel can be used as the monitor-preset channel. In addition, the monitor channel assignment can be changed from the spec command line with counter_par(), as described in the FUNCTIONS section below.

The scale factor is ignored for the time-base channel, since the time base is set and accounted for internally in the C code.

Values for the optional parameters "filter" and "prescale" can be set on the optional counter parameter screen accessed by typing the p command. Enter the parameter name and a value. Possible values are described in the FUNCTIONS section below.

Also, the "active_low" and "io_config" controller parameters, which are not associated with a particular channel, can each be set as an optional scaler parameter for any scaler associated with the controller. When set as a scaler parameter, the value can be modified using counter_par() from the spec command line. Configuring as a scaler parameter overrides the controller parameter setting and behavior.

THEORY OF OPERATION

One of the key requirements for counter/timers in spec is the capability to have a master channel that will gate the slave counter channels by way of a hardware signal. A second requirement is that at least two channels (one for time and one for monitor) can be used as the master channel. Even better is hardware that allows any channel to be used as the master channel. The NI 63xx boards meet these requirements.

The 63xx card architecture allows any channel to be configured to use any other channel's associated gate input pin as its own gate. spec requires each possible master counter's output to be connected to its associated gate via a jumper. That counter's output will then serve as gate for all the counters. See the Hardware Configuration section below.

Normally all outputs are disabled and set to a high impedance state. When a particular counter is the master, spec configures just that channel to have its output activated during counting to serve as gate for all channels. When the master counter counts down from its preset and reaches zero, the last count changes the state of the output, which disables the slave counters. This achieves a reliable hardware gating.

If the card is set up as only counters, spec configures the card so that all channels will gate off the gate pin associated with the lowest numbered channel included in the config file. The external gate from the master timer device can be connected to that pin.

If the 63xx is to be used as master to gate other cards, one must connect the various designated output pins of the possible master counter channels together and use that signal. spec will only activate one output pin at a time. All the other pins will be in the default power-on high-impedance state, so there is no danger of overloading the outputs as long as spec is used to control the card.

By default, spec programs each channel for an active-high gate. That is, during counting the output signal from the master channel will be nominally at +5V. If it would make gating other devices more convenient, the counter_par() command can be used to configure the gate signal as active low (see below).

Although hardware gating is preferred for counters, spec does in any case send appropriate commands to arm and disarm the counters in the absence of hardware gating. The arm command occurs before the master timer is started. The disarm command occurs after the master timer has stopped.

HARDWARE CONFIGURATION

For each counter channel that will be used as a master timing channel (either with the internal time base or with an external monitor-count preset), you need to connect the associated output pin to the associated gate pin. It doesn't hurt to make all the connections, even if you don't anticipate the channel being used for a monitor preset channel. spec uses the conventional pin assignments for the counter input, output and gate connections. These pins are the PFI lines numbered 0, 1, 3, 4, 5, 6, 8, 9, 12, 13, 14, 15. (That is, all but 2, 7 and 10.) All models should have the following connections:

Out(0) pin 2 to Gate(0) pin 3

Out(1) pin 40 to Gate(1) pin 41

Out(2) pin 1 to Gate(2) pin 10

Out(3) pin 5 to Gate(3) pin 39

For boards with two connectors, the pin numbers refer to connector 0. Note, a master timing channel will not work properly until its corresponding output-to-gate jumper is installed.

Input signals connect to the following pins. One channel will probably be used for the time base, as selected in the config file. There's no need to connect an input signal to that channel, since it will be programmed to use the internal clock.

Source(0) pin 37

Source(1) pin 42

Source(2) pin 11

Source(3) pin 6

Choose any of the many ground pins (4, 7, 9, 12, 13, 15, 18, 35, 36, 44, 50, 53) as ground.

FUNCTIONS

The following counter_par() options are available. The first three commands are associated with particular counter channels:

counter_par(mne, "monitor")

Sets the channel assigned to mnemonic mne to be the monitor preset channel. The monitor channel gets reset when the config file is read on start up or on reconfig.

counter_par(mne, "prescale" [, how])

Without the optional argument, returns 2 if the channel for mne has been configured with the divide-by-two prescale and returns 8 if the divide-by-eight prescale has been selected. If called with how set to 2, turns on the divide-by-two prescale. If set to 8, turns on the divide-by-eight prescale. If set to zero, turns off prescaling. The "prescale" parameter can be set as an optional scaler parameter using the hardware configuration editor. If the parameter is not set in the config file, rereading the config file resets the mode to prescale off.

counter_par(mne, "filter" [, val])

The boards have three possible input filters: small, medium and large. Filters are as follows:

Value	Rejects Pulses	Delays Pulse	Adds Jitter
"small"	< 100 ns	100 ns	25 ns
"medium"	< 6.4 us	6.4 us	25 ns
"large"	< 2.54 ms	2.54 ms	10.025 us

The "filter" parameter can be set as an optional scaler parameter using the hardware configuration editor. If the parameter is not set in the config file, rereading the config file resets the mode to filter off.

The following options are associated with the operation of the card, not with a particular channel. The mne argument is necessary for the syntax of the command and should be the mnemonic or counter number of any of the configured channels associated with the card. The DIO bits are 0 to 7 or 0 to 31, depending on what is available on the particular card.

counter_par(mne, "active_low" [, how])

Without the optional argument, returns nonzero if the counting card associated with channel mne has been configured for active-low gates. If called with how nonzero, turns on the active-low mode for gating. Otherwise, sets the default active-high gate mode. The mode only needs to be set for one channel to affect all channels on the card. The "active_low" parameter can be set as an optional controller parameter from the Devices screen of the hardware configuration editor or as an optional scaler parameter from the Scaler screen. When set as a controller parameter, its value cannot be changed using counter_par(). If the parameter is not set in the config file, rereading the config file resets the mode to active low off.

counter_par(mne, "io_config" [, val])

Bits set in val will be configured as outputs on the digital I/O lines. On power up, all lines are configured as inputs. If the optional argument is missing, spec will return the current value as set by the user. (The value can't be read from the card itself.) The "io_config" parameter can be set as an optional controller parameter from the Devices screen of the hardware configuration editor or as an optional scaler parameter from the Scaler screen. When set as a controller parameter, its value cannot be changed using counter_par(). The configured value for "io_config" is saved across readings of the config file.

counter_par(mne, "set_bit", val)

Set output lines corresponding to bit number val to high, where bits and lines are numbered from 0 to 7 or 31 (depending on the number of DIO lines). Set bits are saved across readings of the config file. For example,

counter_par(sec, "set_bit", 5)

would set bit 5 to a high state, if bit 5 has been configured for output.

counter_par(mne, "clr_bit", val)

Set output line corresponding to bit number val to low, where bits and lines are numbered from 0 to 7 or 31 (depending on the number of DIO lines).

counter_par(mne, "put_bits", val)

Sets output lines corresponding to the bits set in val to high and bits not set in val to low. Set bits are saved across readings of the config file. For example,

counter_par(sec, "put_bits", 0x13)

would set bits 0, 1 and 4 to a high state, if the bits were configured for output.

counter_par(mne, "get_bit", val)

Returns 0 or 1 based on whether the input line corresponding to bit number val is high or low, where lines and bits are numbered from 0 to 7 or 31 (depending on the number of DIO lines).

counter_par(mne, "get_bits")

Returns an 8-bit or 32-bit value (depending on the number of DIO lines) that reflects the setting of the input lines.