Appendix B - Impulse Advanced Programming
B-2
Byte Receive Time Out
Since there is no end of transmission frame deliminator, the Impulse assumes if no bytes are received
for 60 ms, the transmission is complete. The receive time out is reset on every byte received
therefore, the host system must insure that the latency between transmitted bytes is less than 60 ms.
Receive Buffer Overrun
The Impulse receive buffer is 25 bytes however, there are no valid transmission frames of this length.
Reading and Writing Parameter Data
The Impulse does not support continuous data streaming due to its condensed receive buffer.
Therefore, the host system must wait for a drive response before sending additional read or write
transmission frames.
Read Queries
The following example illustrates a read request of parameter index #113 (Commanded Position)
from unit #2. Bytes are shown in hexadecimal format.
After sending the read request, the host system would need to wait for the drive to respond before
sending another read query or write request. The drive responds to a read with unit address,
parameter index, data and checksum. Assuming the commanded position is 25000 steps, the
response would be as follows:
Since Commanded Position is a 32-bit value, the data field in the transmission frame is 4 bytes (2
words).
02 F1 F3 00
Checksum Upper Byte
Checksum Lower Byte (Address + Index)
Read Parameter Index (113 + 128)
Unit Address #2
Checksum Upper Byte
Checksum Lower Byte (Address + Index)
Cmd Position Upper Byte, Upper Word
Cmd Position Lower Byte, Upper Word
Cmd Position Upper Byte, Lower Word
Cmd Position Lower Byte, Lower Word
Parameter Index 113
Unit Address #2
02 71 A8 61 00 00 7C 01