Time-Critical Tasks - Jäger ADwin-Gold Hardware Manual

ADwin

5.3 Time-Critical Tasks

For extremely time-critical tasks you can use instructions with which you have
direct access to the control and data registers of the ADC and DAC (see
ADbasic manual). These registers can be found in the memory address area
of the ADSP (memory mapped). These instructions also allow to optimize the
program structure (s.b.).
Contrary to the standard instructions
tions for direct access do not have any test routines. Before you use them
we recommend to learn more about time sequences, progam structures and
functions sequences in an ADC.
5.3.1 Analog Inputs and Outputs
The standard instructions ADC() and ADC12() consist of a sequence of several
instructions (see below). They need a certain time for execution.
SET_MUX()
...
START_CONV()
WAIT_EOC()
READ_ADC() or READ_ADC12()
You can use (or extend) the waiting times wasted in the standard instructions
for other purposes by using the individual instructions. If you apply these
instructions skilfully you may be able to execute faster measurements.
It is important to set the START_CONV() instruction in a sufficient time-delay
from the SET_MUX() instruction, in order to consider the multiplexer settling
time (see also ADbasic manual, „Instruction Reference").
Use the waiting times for instance for arithmetic operations and save CPU
time:
– Settling time of the multiplexer: At a maximum voltage jump of 20 Volt it is
6.5 µs (max.) for the 16-bit ADC and 1.5 µs for the 12-bit ADC.
– Conversion time of the ADCs: It is 0.8 µs for the 12-bit ADC and 8 µs for the
16-bit ADC.
Direct Register Access
A measurement can be executed very fast, when you directly access the control
and data registers of the ADC.
If you have made sure that at the analog outputs the values are within the range
limits, you can write very quickly into one or more DAC registers with direct
access to the hardware registers, and you can synchronously start the output
(see ADbasic manual).
The hardware addresses for the direct access to the control and data registers
are described on the following pages.
ADwin-Gold Hardware Manual, Version 2.3
,
ADC() ADC12()
'wait for settling time
'wait for end of conversion
and the instruc-
DAC()
5.3 Time-Critical Tasks
ADC() and ADC12()
Program structure
ADC
DAC
19