SDL09 configuration

AT commands

  • ATA: sets the device into online/data mode.

  • ATg or ATG: defines whether interfering RF signals are present. SDL sweeps the operating band and provide a display of mean and peak signal levels, in dBm.

  • ATN: provides a detailed scrutiny of the RF environment. The specific start and stop frequencies, along with step size and dwell time are definable. An ATN command example is ATN 905.250 908.500750 25 100, where:

    • 905.250 is the start frequency in MHz up to 6 decimal digits.

    • 908.500750 is the stop frequency in MHz up to 6 6 decimal digits.

    • 25 i the step increment in kHz, it can be from 1 to 1000.

    • 100 is the dwell time in ms, it can be from 1 to 1000.

  • AT&Fn: where “n” is a number, it establishes a default configuration.

    • AT&F1 - Mesh Primary Coordinator

    • AT&F2 - Mesh Remote

    • AT&F3 - Mesh Secondary Coordinator

    • AT&F7 - PMP Master

    • AT&F8 - PMP Slave

    • AT&F9 - PMP Repeater

    • AT&F10 - PP Master

    • AT&F11 - PP Slave

    • AT&F12 - PP Repeater

    • AT&F13 - PMP Master 57k

    • AT&F14 - PMP Slave 57k


    • Mesh Primary Coordinator - Each Mesh network must have a primary coordinator. The primary coordinator provides the synchronization for the network.

    • Mesh Secondary Coordinator - Secondary coordinators can be deployed to extend the range of the Mesh network. Each device on a Mesh network must have LOS (Line of Sight) with either a Primary or Secondary Coordinator.

    • Mesh Remote (Slave) - Any device on the network that is not a Primary or Secondary Coordinator, generally attached to end devices. Can also be used to perform routing tasks if enabled.

    • Master (PMP/PP) - Only one per network. In PP/PMP network types (see S133) data either originates at, is destined to, or passes through the Master.

    • Repeater (PMP/PP) - May act simply as a ‘Repeater’ to store and forward data to/from an upstream unit to/from a downstream unit (e.g. when there is a long distance between units), or, may act as a Repeater/Slave in which case the above function is performed AND the unit may also exchange data as a Slave within the network.

    • Slave (PMP/PP) - Interfaces with remote devices and communicates with Master either directly or via Repeater(s).

  • AT&V: displays all visible S registers and their current values.

  • AT&V1: displays the complete set of user parameters (for advanced users).

  • AT&W: writes configuration into non-volatile memory

  • AT&WA: writes configuration into non-volatile memory and sets the device in online mode.

  • ATSxxx?: displays the xxx register.

  • ATSxxx=yyy: writes value yyy in register xxx.

  • ATSxxx /?: displays the xxx register settings (if they are available).

  • ATIn: where n is one of the following numbers.

    • 0 User string. Use ATI0=<string> to save the string.

    • 1 Product Code

    • 2 Firmware CRC check

    • 3 Product Identification (Firmware Version)

    • 4 Firmware Date

    • 5 Firmware Copyright

    • 6 Firmware Time

    • 7 MAC Address

    • 11 Statistics

    • 18 Error log

    • 19, 20 Mesh Timing information.

    • 255 Factory-Configured Options listing.

  • ATlogin: enables a password to access command mode.

  • ATM: provides information about mesh, such as the current routing table, routing logs and errors.

AT registers

The most of configurations is defined by registers, which are compound of the letter “S” and a number.

  • S0: selects the mode that the device will hace when starting up.


    • 0 - command mode

    • 1 - Data mode

  • S2: ascii value for the character that will be used for escape detection.

    • It can be from 0 to 255. 0 disables the scape detection.

    • 43 (character “+”) is the default value.

  • S80 (with mesh configuration): TX profile. In a mesh configuration where multiple repeaters are transmitting, it is required to establish a ranking system for areas to decide connections and avoid overlappings.

    The first transmitting area is ranked as 1, the second as 2 (repeating 1), the third as 3 (repeating 2), the fourth as 0 (repeating 3) and the following one starts again as 1, repeating the cycle ad infinitum.


    • 0 - It disables TX Profiling, so any radio can send data. This is the default configuration, since TX profiling is generally only useful in partially overlapping coverage areas where collision rates are high.

    • 1 - It allows the bandwidth to be split equally between the Primary Coordinator and all rank 1 units. This may be useful in system where there are no secondary coordinators, as there are no frames assigned to any units other than the Primary Coordinator and associated units

    • 2 - It allows rank 1 units to have 1/2 of the bandwidth. The rest of the bandwidth is split between rank 2 and rank 3 modems. This profile is used when the primary Coordinator is generally located in a location that provides the greatest coverage, meaning it generally has the most units associated with it.

    • 3 - Allocates most of the bandwidth to Rank 1 units. This profile is used in systems with no additional coordinators, where the units send data the majority of the time, with the occasional transmission from the primary.

  • S81 (with mesh configuration): threshold to assess whether a channed is signal or noise. It is expressed in dBm.

    • 60 is the default value.

  • S83: is the ‘Time to Live’ in seconds. SDL averages the last 8 measurements, but if they are not renewed in this time, they are deleted. This time can be from 10 to 65535.

    • 30 is the default value.

  • S85 (with PP or PMP configuration): distance from master repeater to slave repeater (in kilometers) to take into account delays. It can be from 0 to 255.

    • 3 is the default value.

  • S86 (with PP or PMP configuration): distance from master repeater to furthest repeater (in kilometers). It can be from 0 to 255.

    • 3 is the default value.

    • 255 means no slaves will be transmitting any packets.

  • S87 (with mesh configuration): enables using S105 as modem’s units address in Mesh.

    • 0 - Disable. Default value.

    • 1 - Enable.

  • S101 (with mesh configuration): function that SDL will do.

    • 2 - Remote. The device will not act as coordinator.

    • 4 - Primary coordinator. The device will manage the network to synchronize it.

    • 5 - Secondary coordinator. The device will extend the network range.

    • 6 - Stanby coordinator. The device can take over the primary coordinator.

  • S101 (with PP or PMP configuration): function that SDL will do.

    • 0 - Master. Data originates or passes trhought the master. Only one master can exist in a PP/PMP network.

    • 1 - Repeater. SDL sends data received from RF, it can also exchange data as a slave.

    • 2 - Slave. The device communicates with the master (directly or through repeaters).

  • S102: serial baud rate for serial communications. The data rate must be the same for the serial device connected to SDL. When forcing to Command Mode, the data port will temporarily communicate at the default value.

    Values (bps):

    • 0 - 230400

    • 1 - 115200

    • 2 - 57600

    • 3 - 38400

    • 4 - 28800

    • 5 - 19200

    • 6 - 14400

    • 7 - 9600 (default)

    • 8 - 7200

    • 9 - 4800

    • 10 - 3600

    • 11 - 2400

    • 12 - 1200

    • 13 - 600

    • 14 - 300

  • S103: Wireless Link rate at which RF communications will occur. All radios within a particular network must be configured with the same wireless link rate. Faster link rates sacrifice sensitivity.

    Values (bps):

    • 0 - 172800 (default)

    • 1 - 230400

    • 2 - 276480

    • 3 - 57600

    • 4 - 115200

  • S104: Network address as ID. All modems in a given network must have the same address.

  • S105: Unit address. Unique identifier for each radio in a network. It can be from 1 to 65534.

    • 1 - Address for master.

    • 65535 - Broadcast address.

  • S106: Hop pattern. It defines the pattern that SDL will follow to change frequency. The pattern must be the same for master or repeater linked (except for roaming). This register can be from 0 to 49, with 0 as default.

  • S108: Output power. Trasmission power for the antenna in dBm, it should be as low as possible while the fade margin is appropiate. It can be from 20 to 30.

    • 30 is the default value (equivalent to 1 W).

  • S109 (only for masters with PP or PMP configuration): Hop interval. It defines the rate to change frequency for all radios in the same network. Long intervals have large throughput. Short intervals have low latency and are more reliable to interferences. It can be from 0 to 61, with 20 as default.

  • S110: Data format on the serial port. The value must match with the serial device. When forcing to command mode, SDL will temporarily communicate at the default value. When returning to Data Mode, the configuration will take again the values from S102 and S110.



Stop bits

Data bits

































  • S111: Packet minimum size. This is the minimum number of collected bytes in one buffer, before the buffer can be closed by the character timeout (timer controlled by S116). It can be from 1 to 225, with 1 as default.


    It is STRONGLY advised not to modify this parameter, since changing S111 may prevent the SDL from detecting the escape sequence.

  • S112: Packet maximum size. It defines the number of bytes from the connected device that will be encapsulated into a packet, unless the timer S116 expires. Large packets produce better data throughput; however, small packets are less likely to become corrupted, with less impact in that case. It can be from 1 to 256, with 256 as default.

  • S113: This register determines the maximum number of times that a packet will be retransmitted (in addition to the initial transmission). Retransmissions provide system robustness and ensure data delivery. Retransmissions create additional traffic. It can be from 0 to 254, with 254 as default.

  • S115 (with mesh configuration): Repeat interval. It defines the difficulty to access the RF channel. The bigger the number, less attempts are required to access, but the latency will be larger. It can be from 0 to 255, with 5 as default.

  • S115 (with PP or PMP configuration): Repeat interval. It defines the number of slots which are available within a window of opportunity for remote units to submit channel requests to the Master. Remotes will randomly contend for the ability to access the channel request slots. For a small number of Remotes, it is advisable to keep S115 closer to the default value so as to not ‘waste bandwidth’ by maintaining a relatively large window housing a greater-than-necessary number of channel reservation request slots. It can be from 0 to 255, with 3 as default.

  • S116: Character Timeout in quarters of character time. It can be from 10 to 255, with 10 as default (2.5 character time). Radio Link will accumulate data in buffers from the serial port, until one of the following conditions occur:

    • The Maximum Packet Size (S112) has been accumulated.

    • Minimum Packet Size (S111) has been accumulated AND the Character timeout (S116) has expired.

    After that, the message is sent through RF.

  • S118 (with PP or PMP configuration): synchronization with master or repeater. The default value is 1.


    • 65535: SDL will synchronize with an upstream unit which has the same network address (S104). If that upstream unit fails, it will attempt to synchronize with another upstream.

    • From 1 to 65534: specific address to synchronize.

  • S123: average signal strength received over the previous 8 hop intervals, from -110 to -55 dBm.

  • S124 (master with PP or PMP configuration): average signal strength received over the previous 8 hop intervals from a slave or repeater. It can be from -110 to -55 dBm.

  • S126 (with mesh configuration): Attempt before routing again. Number of failed transmissions bofre trying to route again. It can be from 1 to 255, with 9 as default.

  • S130: if it is enabled, it allows to receive and keep data from serial port while the modem is searching for synchronization. This setting does not apply to master and primary coordinator. Should normally be disabled to prevent accumulation of stale data inside a modem.


    • 0 - Disabled (default).

    • 1 - Enabled.

  • S133: Network Type. This register must be set to the same value on every unit in the RF system.


    • 0 - Point to Multipoint. A single master radio broadcasts data to all units, and all remote units send data to the master.

    • 1 - Point to point. Communication between a Master and a Slave. One or more repeaters can be employed.

    • 2 - Mesh. Radios can communicate with each other directly or through another mesh node, without all data being routed through a master.

    • 3 - Mesh with Roaming. Similar to option 2 (mesh), with a difference: a remote radio may join networks with different S106 and S180.

  • S140: Destination address. Ultimate destination for a radio.

    • In a Mesh system, the destination address is entered in MAC address format.

      • For broadcast operation, use the value FF:FF:FF:FF:FF:FF.

      • For unicast operation, the factory assigned MAC address of the destination device must be used, or S105 if S87 = 1.

    • In PP or PMP, the value can be from 1 to 65535, where 65535 is broadcast.

      • PMP - Master S140=65535 and Remote S140=1

      • PP - Master S140=UA of Remote and Remote S140=1 (Master)

  • S141 (mater with PP or PMP configuration): registers the presence of repeaters in the network.

    • 0 - No repeater

    • 1 - 1 or more repeaters.

  • S142: Serial channel mode for the data port.

    • 0 - RS-232 (default)

    • 1 - RS-485 half duplex

    • 2 - RS-485 full duplex


    The radio module of SDL is able to transmit through RS-485, but SDL itself is not built to operate with RS-485. The register S142 must not be changed and keep as 0.

  • S143: Sleep mode. Values:

    • 0 - The radio is always active.

    • 1 (only on remotes) - SDL stays on for at least S145 seconds. After that, it goes to sleep if all data including over the air is sent. The radio will wake up in S144 seconds. Upon wake up the modems will be out on sync with the network and need time to re-synchronize

  • S144: Sleep time in seconds. If Sleep mode is enabled in S143, the radio will go to sleep for S144 seconds. It can be from 2 to 65535, with 60 as default.

  • S145: Wake time in seconds. If Sleep mode is enabled in S143, the modem will stay awake for S145 seconds if all conditions of S143 are met. It can be from 1 to 65535, with 10 as default.

  • S146: Tx Done timeout in quarter of chart. This register along with Modbus RTU setting of S217 can be used to insert a gap between individual packet coming out of the serial port. It can be from 0 to 255, with 14 as default (3.5 characters).

  • S151 (with mesh configuration): when coordinators first come online, they send out a number of quick sync packets, defined by S151, used to quickly attain network synchronization. Each quick sync packet is sent on a random channel listed in the hop pattern. The more sync packets sent, the quicker network synchronization occurs, but at a cost of delayed data transmission. The lower the number of packets sent, the less likely the entire network will synchronize during the quick sync process, resulting in slower overall synchronization. It can be from 5 to 65534, with 500 as default.

  • S153: if this register is enabled with 1, the radio will prepend each packet received from RF with 10 bytes of the following data (in the same order):

    • First 2 bytes - size (high byte first)

    • One byte - RSSI

    • One reserved byte (0x00)

    • Last six bytes - source unit address (high byte first).

    By default, this register is set as 0 - disable.

  • S158: FEC method. FEC consumes significant bandwidth: depending on which coding rate is chosen, a number of coding bits are transmitted along with the data bits. In noisy or long-range communications environments, FEC may effectively increase throughput by decreasing the amount of packet retransmissions which would otherwise be required. FEC may extend RF communications range: at a certain distance where data would otherwise be unacceptably corrupted, employing FEC may be all that is required to maintain the integrity of that data at that distance.




    Information rate

    Number of corrected bits


    No FEC






    1 out of 7


    Hamming (15,11)


    1 out of 15


    Hamming (31,24)


    1 out of 31


    Binary BCH (47,36)


    2 bits


    Golay (23, 12, 7)


    3 bits


    Reed-Solomon (15,11)


    2 nibbles

  • S163: it enables CRC16 checking of received data on local diagnostic port. Note that even if disabled, the incoming data must have two dummy bytes transmitted in place of crc bytes.

    • 0 - Disable.

    • 1 - Enable (default).


    Disabling CRC check is only advisable during troubleshooting of the user’s diagnostic requests.

  • S180: Hop zone. This register allows the use of hopping zones to restrict the hopping table to a specific segment of the 900 MHz ISM band. The default is to populate the hopping pattern/table using channels or frequencies from the entire 900MHz ISM band.


    • 0 - Use the entire ISM band (default).

    • 1 to 10 - Use the band according to register S180.


Additional zones can be seen by displaying help for the S180 register.

  • S181 (with PP or PMP configuration): allows the use of hopping zones to restrict the secondary hopping pattern to specific segments of the 900 MHz ISM band. Any downstream units connected to this will need to have their S180 (Primary Hop Zone) set to same value as the Secondary Hop Zone of the Repeater they are connected to.

    0 - Use the entire ISM band (default). 1 to 10 - Use the band according to register S181.


Additional zones can be seen by displaying help for the S181 register.

  • S183 (with PP or PMP configuration): The period of DCD pulses on synchronized slaves in &C3 mode.


    • Minimum: 1

    • Maximum: number of channels in a hop pattern minus one

    • Default: 5

S183 = 1 - will pulse every hop interval, if S183 = 3 - every third, etc. The counter starts at hop index 0. It is used in some applications to generate common synchronization on many slaves. With the default setting of 5 and the hop interval of 20ms, each slave will synchronously generate a pulse of approximately 3ms every 100ms. * S184 (with mesh configuration): is used to age data in mesh networks in 10 ms ticks. It can be from 1 to 65535. The default is 65535 (never age). * S206 (with PP or PMP configuration): Secondary Hop Pattern. This register, together with the Network ID and the Secondary Hop Zone, determines the secondary hopping pattern that a SDL repeater will use to synchronize and communicate with downstream units. The S106 (Primary Hop Pattern) register must be set to the same value on each repeater/slave that is downstream of this unit. It can be from 0 to 49, with 1 as default. * S214 (with mesh configuration): defines the number of aloha slots available in a Mesh Frame. A slot is a set period of time required to transmit the shortest packet (RTS, CTS, ACK). Increasing the number of aloha slots allows more time for a modem to transmit data during a Mesh Frame. The number of aloha slots directly impacts the hop interval, the more aloha slots, the more time to transmit data, but also the longer the system sits on a single frequency. Reducing the number of aloha slots creates a shorter hop interval which results in a system more immune to interference, but too short an interval may disable communication if devices do not have time to transmit.

It can be from 1 to 255, with 60 as default.


Aloha slots are used for all data communication. When the channel access mode is set to Aloha, the transmitting modem randomly selects a Aloha slot within any frame to begin its data transmission.

  • S215 (with mesh configuration): defines the number of synchronization slots available in a Mesh Frame. In systems with many coordinators, additional slots may be required to avoid collisions. Register S216 can also be used to provide randomness in sending sync packets to avoid collisions. S215 must be set to the same value for each modem on the network or the unit will not synchronize. The value can be from 1 to 10, with 1 as default.

  • S216 (with mesh configuration): defines how often the coordinator transmits synchronization packets. After each synchronization packet transmission the coordinator picks a random number from 1 to the value in S216 and transmits the next packet in this slot. 1 - every synchronization slot, 2 — on average once every 1.5 slots, 3 - on average once every 2 slots etc.

  • S217: Protocol type. Defines how data is sent as output on the local serial port. When Modbus RTU is enabled, there is a delay between the packets coming out of the serial port. The register S146 defines the delay between individual packets.


    • 0 - Transparent Serial (default)

    • 1 - Modbus RTU

  • S218 (with mesh configuration): Input framing type. Controls how the radio treats data coming to serial port. It allows the destination address to be embedded into the data stream, which is automatically stripped by the SDL before transmitting the packet.


    • 0 - Transparent Serial (Default)

    • 1 - Destination Address (DA) is in the first six bytes (high byte first) of the packet. The radio strips these six bytes and doesn’t transmit them. For example, if the DA is 01:23:45:67:89:AB then the high byte is 0x01,the lowest byte is 0xAB. Note that the max size of the data itself in this case is S112 minus 6. If S112 = 256 then the max data size is 250 bytes.

  • S219 (with mesh configuration): Routing request TTL. Routing Request Timeout in 10 ms ticks. (1-10000). The default is 10, which is 100 msec. This defines how long a unit will wait for a Routing Request to provide possible routes. During this time no other data may be sent from the unit. Setting this value too low may not give the system enough time to report the best path, alternately, a value too high may create latency in the system as it waits for the TTL to expire before allowing data transmission, although it has already received the best path. It can be from 1 to 10000, with 10 as default (which lasts 100 ms).

  • S220 (with mesh configuration): Mesh coordinator rank. Used with Tx Profiles. It can be set from 0 to 3 or 255. Value of 255 (default) is for automatic ranking.

  • S221 (with mesh configuration): Aloha slot number in mesh TDMA (Time-Division Multiple Access), where the radio will start its transmission in Tx On Slot channel access mode S244 = 2. It can be from 1 to 255, with 1 as default.


    When register S244 = 2, the Channel Access Mode is set to TDMA. In this mode each radio in the system starts its transmission on an assigned slot number within the frame. The slot number is defined by S221.

  • S222 (with mesh configuration): Roaming mode.


    • 0 - Disabled. A mesh radio will synchronize only to a coordinator with the matching set of S106 and S180.

    • 1 - Roaming on Zone/Pattern.The radio will synchronize with any valid coordinator.

  • S223 (with mesh configuration): Routing. This register is used to enable or disable the Mesh Routing function of the radio. Whenever coordinators are added to a system, routers are typically required in a network. Any unit in a Mesh network can be used to perform routing tasks. Although it is a good idea to have more than a single router, too many routers may create unnecessary traffic in the system.


    • 0 - Disabled - Disabled by default

    • 1 - Enabled - Routing can be enable on any unit, but the more units performing routing tasks, the more routing traffic generated.


    For Mesh Networking to be an effective networking topology, routing functions must be performed to discover paths within the network to each destination, to ensure the best path is chosen. All units in a Mesh Network, including remotes, can be configured to provide routing capabilities by setting register S223.

  • S224 (with mesh configuration): Standby trip level. Synchronization level of mesh standby coordinator to become the primary coordinator. This register works with the syncrhonization timeout (S248) on the primary coordinator to monitor the synchronization level to determine when the Primary Coordinator has failed. The synchronization timeout sets a counter (set by S248 on the Primary coordinator and propagated in synchronization packets) that counts down each time a frame is received that does not contain synchronization data from a coordinator. If the unit receives synchronization data the counter is reset, if the counter reaches zero the unit will lose synchronization.

    Values: from 0 to 255, with 20 as default.


    The standby trip level (S224) is designed to be able to transition a standby coordinator to a primary coordinator before the network loses synchronization. This is accomplished by watching the counter set by S248 and triggering at the level set by S224.

  • S225: Compression. Using compression may improve overall performance of the modem.


    • 0 - Disabled.

    • 1 - Enabled (default).

  • S232: Maximum number of buffers from the local communications port. It is used to limit the amount of storage that the modem will allocate to incoming user’s data. Each buffer is S112 number of bytes. With S112=256 (default) and S232=200 (default) the modem can store up to 51200 bytes.

    Values: from 1 to 255, with 200 as default.

  • S234 (with PMP configuration): after the master releases the channel, it will wait for the S234 number of hop intervals to allow the slaves to send channel requests before the master arbitrates the channel.


    When many slaves want to request the channel at the same time, setting this register to a bigger number will help to ensure that the channel arbiter in the master will allocate the channel fairly (new modems will be given higher priority over modems that were recently allocated the channel).

    Values: 1 to 254, with 1 as default.

  • S235 (with PP configuration): routing time to live in seconds. It defines the aging interval for routing information in PP Mode.

    Values: from 1 to 65535.

    • 65535 — Never aging.

    • 30- default.

  • S236: maximum buffer out storage. It limits the number of buffers waiting to be output to the user on COM1.

    Values: from 1 to 65535.


    Normally this register should not be changed.

  • S244 (with mesh configuration): channel access mode. This register defines how devices access the channel when they have data to transmit.


    • 0 - Aloha: units use Carrier Sense Multiple Access (CSMA) to access the channel, if available, and send data. Register S115 can be set to configure the randomness at which devices access the channel to avoid collisions. Default for coordinator.

    • 1 - RTS/CTS: when units wish to transmit, they request a channel (RTS) from the associated coordinator. The Coordinator will respond immediately (CTS) if the channel is successfully allocated. Default for secondary coordinators and remotes.

    • 2 - TDMA: transmission on slot. See S221.

  • S245 (with mesh configuration): cost of one hop in mesh routing. When choosing the best route, the cost of each route must be considered. Cost of Hop allows a user to influence the relationship between the cost of RSSI and the Cost of Each hop.

    Values: from 0 to 255, with 100 as default.


    For Mesh Networking to be an effective networking topology, routing functions must be performed to discover paths within the network to each destination, to ensure the best path is chosen. Routing is a key element in Mesh network design that can have a profound impact on overall system performance.

  • S248: synchronization timeout. To remain synchronized to the network, a unit must receive synchronization data occasionally from a coordinator or master. The synchronization timeout defines the number of frames (Mesh) or hops (PMP or PTP), before losing synchronization completely.

    Values: from 4 to 65534.

    • 100 is default for mesh.

    • 512 is default for PP and PMP.


In mesh topology, 248 is only set on primary coordinator and propagated in synchronization packets.

  • S249 (with PMP or PP configuration): it limits the number of packets that a radio can send in one hop interval.

    Values: from 1 to 255, with 255 as default. 255 represents unlimited packets.


    Normally S249 should be left unchanged.

  • S250 (with PMP configuration): It sets a limit on bandwidth available to the master when the channel is allocated to a slave. Its is represented as %.

    Values: from 0 to 100, with 50 as default.

  • S251 (with PMP configuration): it defines the channel release timeout in hop intervals. Normally a slave must release the channel by sending a channel release packet. If slave stopped communicating with master and didn’t release the channel, the master will wait for S251 hop intervals before de-allocating the channel.

    Values: from 1 to 255, with 10 as default.


Normally S251 should be left unchanged.

  • S252 (with PMP configuration): it defines a number of packets a slave can transmit before releasing the channel.

    Values: from 1 to 255, with 10 as default and 255 disables that restriction.