ZWorld Exp-A/D12, User Manual

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Exp-A/D12 Software Reference s 69
General Exp-A/D12 Functions
There are several functions specific to Exp-A/D12 boards in
PLC_EXP.LIB
.
Use the higher level functions that reference the signal table.
• int add_sig_table( int entry, int addr,
int in_ch, int mode, int comp )
Fills in an entry in the signal table.
PARAMETERS:
entry
selects table entry.
addr
is the 12-bit PLCBus address of Exp-A/D12.
in_ch
is the input channel to read (0–7).
mode
is the conversion mode (gain and polarity) (0–17).
comp
1 = use EEPROM compensation coefficients,
0 = no compensation.
RETURN VALUE:
0 signal data successfully entered in table
–1 EEPROM hardware error
–2 EEPROM write-protect error
–3 invalid parameter used
• int plcad_addr( int board )
Returns the 12-bit (nibble-interchanged) bus address for an
Exp-A/D-12 board identified by
board
, a logical address (0–63).
A/D Conversion
• float ad_conv( int entry, int value )
Returns the voltage represented by a 12-bit A/D input
value
, assum-
ing a 2.5 V scale. The term
entry
identifies the signal in the signal
table. If the signal table entry specifies compensation for the signal,
the function computes its value using the entry’s calibration coeffi-
cients, otherwise it uses a standard set of coefficients.
• int plad_rd12( int mode )
Returns a 12-bit A/D value read from the A/D converter chip.
mode
specifies one of the A/D conversion modes (0–17) to use.
To use this function, make sure that (1) the address of the Exp-A/
D12’s B register is placed on the bus and (2) one of the eight input
channels has been selected.
Higher level functions are available.