ARF169 Radio Modems - User guide version V1.4
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3.2. Continuous asynchronous protocol
3.2.1 Description of the protocol
The continuous asynchronous protocol enables data transfer from the UART interface to the radio link with the lowest possible latency. It is
associated with radio modulations enabling a wide range of air data rate and ranges to be covered. This is the mode that will allow you to use
the ARF169 modem to the maximum of its possibilities.
• In transmission, data entering on the UART is immediately transmitted into the “air”.
• In reception, data from the RF frames is transmitted progressively to the UART interface.
There is no buffering of complete radio frames before or after transmission on the serial link.
However, the product has buffering enabling a buffer to be performed if the radio and UART data rates are different. The UART interface does
not require a specific protocol. Each octet transmitted is transferred into the air and vice versa.
Thanks to its low latency and the absence of a protocol on the UART port, the ARF169 modem used with the continuous asynchronous protocol
is completely transparent in the replacement of a wire link.
3.2.2 Implementation
The continuous asynchronous protocol is selected by the S222 register (cf §5.3).
It can use the following radio data rates: 2.4kbps, 9.6kbps and38.4kbps. The adjustment of the radio data rate is done via the S254 register (cf
§ 5.3).
The notions of addressing (broadcast communication, group communication and addressed communication between products) are available and
described below.
3.2.3 Addressing
The product has various addressing modes that are configurable via the product registers. The following modes are available:
• Transparent mode without sub-network
• Transparent mode with sub-network
• Addressed mode without sub-network
• Addressed mode with sub-network
The transparent modes are intended for inter-product communication: all products are recipients of the frames transmitted. The addressed
modes enable communication to one or more products (creation of sub-groups).
Transparent mode without sub-network
• In the Transparent mode without sub-network all products within range receive the frames from the transmitting products. The configura-
tion required for this mode of communication is as follows :
• S220=0 (transparent mode)
• S253=0 (no group)
Transparent mode with sub-network:
The sub-networks enable groups of products to be created that communicate with each other within the same sub-network. Products in sub-
network 1 cannot see those in sub-network 2 and vice versa. On the other hand all the products are visible between themselves within the
same sub-network.
• S220=0 (transparent mode)
• S253=Number of the sub-network varying from 1 to 255
when register S253 is set to 255, the frame is broadcast to the whole of the sub-network.
Addressed mode without sub-network:
In the addressed mode without sub-network a product communicates with a specified addressee. Only the addressee receives the frames from
the transmitting products. The configuration required for this mode of communication is as follows:
• S220=1 (address mode)
• S253=0 (no sub-network)
• S252=local address (16 bit address)
• S256=address of the recipient (16 bit address)
When register S256 is set to 65535, the frame is broadcast and visible by all equipment within range.
