Honeywell Multitrend SX Modbus Master help

Hi,
I've got a Honeywell Multitrend SX paperless recorder that I'm using as a Modbus Master device to poll another I/O device for some analog inputs it contains. Everything seems to be working. I've tested the slave device with a Modbus master simulator and hooked it up to the Multitrend. The LED's and the recorder show successful communication. I want to make the new analog input data into pens on the chart. However, I don't know where to retrieve the data in the recorder. I've scoured the manual and internet to try to find a solution. Anyone know how to solve this? Thanks in advance.

Pete

Yeah, I've done that. Page 87 (pdf) from the recorder manual:

Each slave can perform up to 8 “transactions”,
where a transaction can retrieve or send 1 or more registers from a slave, or retreive
or send 1 or more Pens to a slave. Access to slave registers within the maths function
has been provided using SCV (Slave Comms Variable). For example SCV[x,y,z], where x =
Slave number, y = Transaction Number, and z is the each successive register retrieved​

starting from 1 (Item).

Hence, the pen 'math' statement = SCV[x,y,z]

I seem to recall that the SCV x, y, and z terms are defined in the Modbus master transaction setup at completion of the setup, although the z term might not be individual, but for a range of values, like 1-11 or something like that, so you'd use 1 for the first, 2 for the second, etc.

There's an example on the app sheets, where connection to another Honeywell device is described, one for Modbus RTU over RS-485
http://hpsweb.honeywell.com/NR/rdonlyres/8A10B2E0-41AA-4475-94C8-F830DAD5881E/61411/43TV3397.pdf

another for Modbus TCP,
http://hpsweb.honeywell.com/NR/rdonlyres/982E2285-54C6-40C5-9FF1-B146CD580EB8/61401/43TV3392.pdf

but the way the data is used in a Trendview 'pen' is identical for both and applicable to any Modbus slave device.

Dan