Applied Motion RS-232 - Manual (Page 242)

242 920-0002 Rev. I
2/2013
Host Command Reference
Programmer does support RS-422 in a limited fashion).
• Permits longer cable Lengths
• May require special adaptor
• Immune to EMI (when wired properly)
RS-485 (2-wire RS-485): Designed for multi-drop serial networks, provides simple wiring, high reliability, and
long cable lengths. Here are some RS-485 highlights:
• More difficult to use
• NOT supported by Applied Motion software applications such as Quick Tuner or Configurator. (Q
Programmer does support RS-485 in a limited fashion).
• Permits longest cable lengths: up to 1000 feet at low baud rates
• May require special adaptor
• Fewest wires, smaller cables
• Immune to EMI (when wired properly)
COM Port Settings
UART Settings: We operate our UARTs with the following settings: 1 start bit, 8 data bits, 0 (no) parity bits,
and 1 stop bit.
Bit rate (baud) Settings: (BR and PB commands): All AMP drives default to 9600 baud from the factory.
In most cases this speed is adequate for setup, configuring, programming, as well as host mode communications.
If higher baud rates are required the drives can be configured to operate with a different rate using the BR (Bit
rate) or PB (Power-up Bit rate) command. In all cases the drive starts up at the factory rate, 9600, and will remain
there if the “power-up packet” is acknowledged by the host (see “Drive Startup” below). When the power-up cycle
is complete and if the drive has not received the power-up packet, the drive will activate the new baud rate.
Selecting a baud rate higher than the default 9600 is dependent on the application. If there is a host
device operating a number of drives on a network, a higher speed may be required in order to process all the
communication needs.
Communications Protocol
In general, the protocol for communications between a host device and a drive is quite simple. The drives
do not initiate communications on their own, so drives are normally in a state to receive packets from the host. A
communications packet, or packet for short, includes all the characters required to complete a command (host
to drive) or response (drive to host) transmission. In other words, a host initiates communication by sending a
command packet, and the drive responds to that command (if necessary) by sending a response packet back to
the host.
Command Transmission (host to drive): The transmission of characters to the drive requires the host to
send all the required characters that form a packet in a limited time frame. At the start of receiving a packet, the
drive begins timing the space between characters. Each time a character is received an internal timer is reset
to 200 milliseconds. If the timer reaches zero before the next character in the packet is received the drive will
terminate its packet parsing (characters will still go into the receive buffer) and may send out an error response
packet depending on the protocol setting. The purpose of the time-out feature is to allow the drive to purge its
buffers automatically when a bad transmission occurs.
NOTE: This time-out feature limits the usage of host devices such as the Windows application
HyperTerminal. We recommend using Applied Motion’s SCL Setup Utility instead. This utility sends out an entire
command packet with the minimum delay between characters, and includes the packet’s terminating character
(carriage return).
Command packets are terminated by a Carriage Return (ASCII 13).
Response Transmission (drive to host): In response to a command packet from the host a drive can send
a response packet. The drive sends out its entire response packet with very limited space between characters.