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After the control computer receives the <ACK> it
will see the RTS from the next satellite and again
issue the <ENQ> command. The above process will
be repeated until all satellites are numbered.
If a satellite does not receive valid data from the
control computer or detects a transmission error, it
will send a <NAK>. When the control computer
receives the <NAK> it will resend the
<STX>Pnn<CR> to the satellite. Section 1.10 on
error handling describes the maximum retries the
control computer will perform.
If a satellite is turned on after all the other satellites
have been numbered, it will be numbered the same
as described above with the next available number if
no commands have been sent to the other satellites.
If commands have been issued, the satellite is
assigned a temporary number starting with 89 and
decrementing for each subsequent satellite. This
will cause the satellite to release its RTS so normal
communication can proceed. The operator will be
alerted to the condition that another satellite has
come on-line and needs to be numbered. The
operator will then be able to assign the new
satellites a number so that they will appear correctly
in the system. The control computer will use the
following commands to renumber a satellite:
<STX>PooUnn<CR>
The oo is the old satellite number and nn the new
number.
If a satellite is requesting to be numbered and the
control computer has already issued 25 satellite
numbers, the control computer will assign the
satellite the number 89 as described in the preceeding
paragraph and alert the operator to the situation.
If a satellite is powered down after it has been
numbered, it will be treated as a new unit as
described above when it is powered up again.
1.5 - REMOTE/ LOCAL
OPERATION
Once a satellite is in the remote mode, it can be
returned to local mode using the control computer
and the "L" command. If the control computer
program is no longer running, the satellite can be
powered off and then on to return it to local
operation. If the "L" command is used, the satellite
will retain its assigned number and respond to
request commands from the control computer but
ignore control commands.
1.6 - COMMAND FORMAT
Most commands from the control computer are
preceded with the start of text <STX> character
(02 hex), a satellite identification letter (P for Pump,
M for mixer) and a two digit satellite number
(01 through 89). Numbers 00 and 90 through 99 are
reserved for special cases. When the same
command is to be executed by all pump drives, 99 is
sent for the satellite number. After the command
character is the parameter field which varies in size
from zero characters to 32 depending on the
command. A carriage return <CR>, (0D hex) is
used to indicate the end of a command string. (Note,
the exceptions to this computer issued command
format are <ENQ>, <ACK> and <NAK>.) See
Figure A2.
More than one command can be put in a command
string as shown following:
<STX>P09S+0500.0V08255.37G <CR>
The above multiple command string example would
set the speed at pump satellite 09 to 500.0 RPM,
24
®
clockwise direction, set 8255.37 revolutions and
start the drive. The maximum number of characters
allowed in one pump drive string is 38, including
<STX>, Pnn and <CR>.
1.6.1 - Command Features
1. INITIALIZING
Before a pump drive can be controlled, it must
first be numbered. If any command is issued
before this is done, the satellite will not respond.
2. SETTING SPEED
If a SPEED command is issued after the speed
has already been set, the new speed will be used.
If the pump drive is running and a different
direction is sent to the pump, the pump will send
back a <NAK>. A halt command must first be
issued before the direction can be reversed.
3. SETTING REVOLUTIONS
When "Revolutions To Go" are set with the V
command, they are added to the total revolutions
to go counter. The maximum this counter can be
is 99999.99. If a revolutions to go count is sent to
the pump drive which would cause the counter to
over flow past 99999.99, the pump drive will not
add the value to its revolutions to go counter and
will send the control computer a <NAK>. The
revolutions to go counter can be set to zero by
using the Z command, which will also cause the
pump to stop if it is running when the Z
command is received.
1.7 - CONTROL COMPUTER
PARAMETER FIELDS
The parameter field sent by the control computer is
variable in length. The control computer will have
the option of using leading zeroes, leading spaces,
or no padding at all. For example, if 200 revolutions
was to be sent with the V command, the following
Figure A2
list of parameters would all be accepted by the
satellite as valid:
(s = space)
00200.00
ss200.00
sss200.00
sssss200
200.00
200.0
200
1.7.1 - Satellite Data Fields
Any data that a satellite sends to the control
computer will have a fixed number of characters
which is determined by the command. For example,
if the control computer requested the cumulative
volume, it would always receive 10 characters
representing the cumulative volume (0000000.00 to
9999999.99).
1.8 - PUMP DRIVE STATUS
REQUEST
When the control computer requests status from the
pump drive (I command or <ENQ>), the satellite
will respond with the following status information
(Figure A3):
Note: "Pump not numbered" is also a pump status
but it is not included in the pump status byte
since this condition is handled separately
using the P?x (see section 1.4).
When the satellite sends the status information, any
status conditions that are latched by the satellite will
be cleared by the control computer sending an
<ACK>Pnn<CR>. If the satellite receives the I
command again, it will respond with the same status
information.
Figure A3
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