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3.4 Allocation of buffer memories (BFM)
BFM
*#0
Channel initialization Default = H0000
*#1
Channel 1
*#2
Channel 2
*#3
Channel 3
*#4
Channel 4
#5
Channel 1
#6
Channel 2
#7
Channel 3
#8
Channel 4
#9
Channel 1
#10
Channel 2
#11
Channel 3
#12
Channel 4
#13-#14 Reserved
Selection of A/D
#15
conversion
speed see note 2
BFM
#16-#19 Reserved
*#20
Reset to Defaults and Preset. Default = 0
*#21
Offset, Gain Adjust Prohibit.
*#22
Offset, Gain Adjust
*#23
Offset Value
*#24
Gain Value
#25-#28 Reserved
#29
Error status
#30
Identification code K2010
#31
Cannot be used
(1) Channel Selection
Channel initialization is made by a 4 character HEX number HOOOO in buffer memory BFM #0.
The least significant character controls channel 1 and the 4 character controls channel 4.
Setting of each character is as follows:
O = 0: Preset range (-10V to +10V)
O = 1: Preset range (+4mA to +20mA)
Example: H3310
CH1: Preset range (-10V to +10V)
CH2: Preset range (+4mA to +20mA)
CH3, CH4: Channel OFF
(2) Analog to Digital Conversion Speed Change
By writing 0 or 1 into BFM #15 of the FX
However the following points should be noted:
To maintain a high speed conversion rate, use the FROM/TO commands as seldom as possible.
NOTES: When a conversion speed change is made, BFM #1-#4 are set to their default values immediately after the
change. This is regardless of the values they held originally. Bear this in mind if a speed change will be
made as part of the normal program execution.
(3) Adjusting Gain and Offset values
(a) When buffer memory BFM #20 is activated by setting it to K1, all settings within the analog special function
block are reset to their default settings. This is a very quick method to erase any undesired gain and offset
adjustments.
(b) If (b1, b0) of BFM #21 is set to (1,0), gain and offset adjustments are prohibited to prevent inadvertent changes
by the operator. In order to adjust the gain and offset values, bits (b1, b0) must be set to (0,1). The default is
(0,1).
(c) Gain and offset values of BFM #23 and #24 are sent to non-volatile memory gain and offset registers of the
specified input channels. Input channels to be adjusted are specified by the appropriate G-O (gain-offset) bits
of BFM #22
Example: If bits G1 and O1 are set to 1, input channel 1 will be adjusted when BFM #22 is written to by a TO
instruction.
(d) Channels can be adjusted individually or together with the same gain and offset values.
(e) Gain and offset values in BFM #23 #24 are in units of mV or µA. Due to the resolution of the unit the actual
response will be in steps of 5mV or 20µA.
Contents
Contains the number of samples (1 to
4096) to be used for an averaged result.
The default setting is 8-normal speed. High
speed operation can be selected with a
value of 1.
These buffer memories contain the
averaged input values for the number of
samples entered for the channel in buffer
memories #1 to #4 respectively.
These buffer memories contain the present
value currently being read by each input
channel.
When set to 0, a normal speed is selected
of 15ms/ch (default)
When set to 1, a high speed is selected of
6ms/ch
b7 b6 b5 b4 b3 b2 b1 b0
Default = (0, 1) Permit
G4 O4 G3 O3 G2 O2 G1 O1
Default = 0
Default = 5,000
O = 2: Preset range (-20mA to +20mA)
O = 3: Channel OFF
-4AD, the speed at which A/D conversion is performed can be changed.
2N
In buffer memory locations (BFMs)
marked with an "*" data can be written
from the PC using the TO command.
For buffer memories (BFMs) without "*"
mark, data can be read to the PC using
the FROM command.
Before reading from the analog special
function block, ensure these settings
have been sent to the analog special
function block. Otherwise, the previous
values held in the analog block will be
used.
The buffer memory also gives a facility
to adjust offset and gain by software.
Offset (intercept): The analog input
value when the digital output becomes 0.
Gain (slope): The analog input value
when the digital output becomes +1000.
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