Echelon I/O Model Reference for Smart Transceivers and Neuron Chips - Manual (Page 142)

132 Timer/Counter Input Models
Changes the maximum value for each period measurement for an edgelog
device declared with the single_tc option keyword. The maximum value may
range from 1 to 65535; the default value is 65535.
Example for a Series 3100 device with a 10 MHz input clock: An edgelog input
object using clock(3) and the default maximum period yields a 1.6 μs resolution
and does not overflow until 104.86 ms elapse. Using a value of 7500 for
io_edgelog_preload( ) results in the io_in( ) function call terminating if 12 ms
elapse with no input edges.
Syntax
pin [input] edgelog [single_tc] [mux | ded] [clock ( const-expr )] io-object-name ;
pin
Specifies a Neuron input pin for the edgelog input object. The input pin can
be IO_4 through IO_7 if the single_tc option is specified, otherwise the input
pin must be IO_4.
single_tc
Optionally specifies that a single timer/counter should be used. If this
keyword is not specified, two timer/counters are used. If a single
timer/counter is specified, the application can only be loaded on a device
based on a Series 3100 or Series 5000 Smart Transceiver, a Neuron 3120
Chip, or a Neuron 3150B1 Chip (or newer).
mux | ded
Specifies whether the I/O object is assigned to the multiplexed or dedicated
timer/counter. This option is only necessary with the single_tc option when
the edgelog device is declared on pin IO_4. The multiplexed timer/counter is
always used on pins IO_5 through IO_7.
clock( const-expr )
Specifies a clock in the range 0 to 7, where 0 represents the fastest clock and
7 represents the slowest clock. The default value is clock 0.
You can change resolution for the timer base clock frequency by calling the
io_set_clock( ) function with a clock value in the range 0..7 (using one of the
TCCLK_* macros defined in <echelon.h>). This function overrides the
resolution value specified for clock() within the I/O object declaration.
For an application running on a Series 5000 device, you can specify an
increased resolution for the timer base clock frequency by calling the
io_set_clock() function with a clock value in the range 0..15 (using one of the
TCCLK_* macros defined in <echelon.h>). This function overrides the
resolution value specified for clock() within the I/O object declaration.
See Appendix A,
Timer/Counter Periods and Resolution , on page 187, for a
description of the timer resolution and maximum range for each specification
of the clock() value or each value of the TCCLK_* macros. See the Neuron C
Reference Guide for information about the io_set_clock() function.