Rockwell Automation 1771-VHSC , D17716.5.74 Very High S - Manual (Page 24)

1–16 Overview of the Very High Speed Counter Module
Tying Outputs to Counters
You can jumper any of the outputs to any of the counter inputs on the
module field wiring arm. In this way, it is possible to use the outputs
to reset a counter or to cascade counters. If using the outputs this
way, make certain that the input voltage jumpers are set to interface
with the appropriate output voltage.
Handshaking
A pair of handshaking bits are provided for each counter. These bits
are called New Data (ND) bits in the BTR instruction, and New Data
Acknowledge (NDA) bits in the BTW instruction. They indicate
when a stored data value has been most recently updated. These bits
are provided for count/accumulate applications, but can be used
whenever the stored data is updated at a rate slower than the block
transfer time.
The New Data bit (BTR status word 1, bits 4-7 for counters 0-3
respectively) can be used by the ladder program to indicate that a
store register (BTR words 11-18) has been updated by one of the
following events:
An active gate transition in any of the store count modes
The end of the gate sample period in either the period/rate or
continuous/rate modes
The end of the programmed sample period in rate
measurement mode
The ND bit is reset in the ladder program by a 0 to 1 transition of the
corresponding NDA bit, and then performing a BTW. A BTW length
of 1 word can be use for this handshaking procedure.
Note: A BTW length of 1 has no effect on the preset or reset bits in
BTW word 1, and does not qualify as a configuration BTW. (For
example, if the BTW valid bit is set, it will remain set after the BTW
with a length of 1 is sent.)
A default configuration is built into the module. The default
configuration is automatically selected on power-up if the user has
not configured the module through a Block Transfer Write
Initialization file. The module can be placed in the default
configuration by writing a block transfer write initialization file with
all zeroes to the module.
Default Configuration