Applied Motion 1240i - Manual (Page 10)

SCL Software Manual 10
920-0010 rev B
9/26/07
Command Buffer Overflow
Since buffered commands such as moves can take a long time to execute, other buffered commands must
wait. It is easy to overflow the command buffer if you don’t pay attention. The easiest thing to do is to ask the
drive how much space is available for buffered commands before you send one. You do this with the BS
command. If the BS command indicates that less than 20 characters are available, you should not send more
buffered commands to the drive.
Transmit Buffer Overflow
Some commands return more characters than you send. IS, for example, takes 3 milliseconds to send: one ms
for the “I”, one for the “S” and one for the carriage return that completes the command. When processed by the
drive, IS will put 12 characters into the transmit buffer: for example “IS=10101010<cr>”. Those characters need
12 ms to leave the drive, so if you send a continuous stream of IS commands, the transmit buffer will quickly
overflow. You may see the same data come out of the drive twice, or you may get garbage. It is wise to put
some delay after each status command (IS, BS, RV, IE, IP, etc.) or to wait for the response before asking for
anything else.
Registers
Many SCL commands transfer information to a drive for later use. This information is stored in “registers” and
remains there until a new command changes it or power is removed. For example, if you send the command
“VE10”, the VE register is set for a maximum move speed of 10 rev/sec. You can execute as many FL, FP or
FS moves as you like without sending another VE command - the speed will remain at 10 until you change it.
In addition to the VE register, there are registers for move acceleration and deceleration (AC and DE), move
distance (DI), and jog acceleration and speed (JA and JS). Besides the move parameters, there are registers
for limit sensors (DL), motor current (CC), motor and encoder resolution (MR, ER), motor and encoder position
(SP, EP).
Two special registers are PC (power on current) and PM (power on mode). Unlike the other registers, PC and
PM retain their value even when power is removed from the drive. All other registers are “volatile”, losing their
information at power down, and reverting to default values at power on.
Idle Current Reduction
Any indexer-drive operating in SCL mode automatically reduces the motor current by 50% when the motor is
not moving. If you need an idle current value other than 50%, you will need to use CC command before and
after each move to “manually” set the current. To completely power down the motor, use the MD command.
Analog Inputs
The 1240i, 3540i and Si2035 drives each include one 10 bit, 0 to 5 volt analog input. This input can be read by
the buffered command RA or by the immediate command IA. The RA command provides a decimal response
in volts. The IA command responds with a hexadecimal value between 0 and 3FF that is proportional to five
volts. For analog signal connections, please refer to your drive’s hardware manual.