Holding Registers
Chapter 5 Modbus Protocol
MiniCapt Remote Microbial Air Sampler Operations Manual
Page 5-9
Holding Registers
Like the coils, spares are in place between the “standard” registers and those that are
designated as specific/optional. There are no specific/optional coils defined for the
MiniCapt.
If the sample setting holding registers are sent while the unit is sampling, it will ignore
the new settings until the next sample set is executed.
40001 - 40002:
Real Time Clock
Dual-register representation date & time. Integer value
(type defined as time_t) representing date/time in seconds
since January 1, 1970.
40003:
Sample Interval/Sample Volume
This register representation depends on the Sample
Volume Mode setting (coil 00/09). When the Sample
Volume Mode is disabled - this register represents the
number of seconds to run a sample. When the Sample
Volume Mode is enabled - this register represents the
volume in liters multiplied by 100.
40004:
Hold/Tare Time
Time, in seconds, processed between the pump coming up
to the specified flow and starting the first sample.
40005:
Repeat Count
Number of samples to process. A value must be greater
than 0.
40006:
Delay Time
Time, in seconds, processed between each sample.
40007 - 40032:
Spare
Table 5-3
Holding Registers
Holding Registers
Description (Setup)
Comment
40001
dual
Real Time Clock (high)
time_t
40002
dual
Real Time Clock (low)
time_t
40003
unary
Sample Interval/Volume
Seconds
40004
unary
Hold/Tare Time
Seconds
40005
unary
Repeat Count
Repeat Count
40006
unary
Delay Time
Seconds
Spare
unary
26 spare registers
Reserve future “common” registers
