ProSoft Technology PTQ-AFC - Manual (Page 175)

PTQ-AFC ♦ Modicon Quantum Platform Backplane Communication
Liquid and Gas Flow Computer for Hydrocarbon Products User Manual
ProSoft Technology, Inc. Page 175 of 259
June 23, 2011
The "Slave Selection, register bank, direction" register can assume one of the
following values:
Binary Value Decimal Value Slave Register Type Function
000 0 Primary Holding Read
001 1 Virtual Holding Read
010 2 Primary Input Read
011 3 Virtual Input Read
100 4 Primary Holding Write
101 5 Virtual Holding Write
110 (illegal) 6 (illegal) Primary Input Write
111 7 Virtual Input Write
Function 6 ("primary input write") is always rejected with exception "illegal
function". However, because the virtual slave’s input register bank is treated as
an extension to its holding register bank, function 7 is equivalent to function 5
where the register address is offset by 10000, and the "illegal function" exception
is returned only if the indirect addresses spanned by the request include no
writable registers (as happens also to a function 4 request that spans no
writables).
9.1.5 Modbus Pass-Thru Block
You can configure the Pass-Through registers in the Virtual slave using the AFC
Manager software. After the module receives a Modbus write command from an
external Modbus Master device, it will automatically move the data to the
Quantum processor. This block is optional and must be defined only if the
application intends to use this feature.
The processor should constantly check for incoming pass-thru messages in the
processor through following registers in the Supervisory Input Block:
Offset Description Type Comments
12 Pass-thru transaction pending Status
47 Pass-Thru Transaction 0-word/1-bit select Input
48 Pass-Thru Transaction register address Input
49 Pass-Thru Transaction number of registers Input
Offset 12 (Pass-thru transaction pending) is set to 1 when the module receives a
Modbus pass-thru message from the master unit.