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Understanding Machine Attributes | Nayax Core

Machine Attributes let you control how your Nayax device communicates with the vending machine, accepts payments, reads DEX data, and displays messages, all from a single screen in Nayax Core. This guide covers the main eight attribute groups: Card Readers, Payment, MDB, Communication, DEX/DDCMP, Device Features, LCD, and VMC & Sim Card.

Before you start

1. Card Readers

Configures the core Point of Sale (POS) settings that determine how your device accepts and processes card payments, including MDB communication level, currency formatting, supported card types, transaction triggers, and VPOS button behavior.

Card Reader Settings

Attr #	Name	Default	Purpose
520	Card Reader MDB Level	1 (Basic features)	Sets the MDB communication level for the device. Match to the level supported by your vending machine. Values: 1 = basic, 2 = revalue, 3 = Always Idle state. Device restart required after changing.
523	Decimal Place	-	Controls how currency values are transmitted to the machine over MDB. Same number sent represents a different amount depending on this setting. Also affects Default Credit.
535	Extended Cards Support	-	Specifies which card networks and standards the device accepts. Set based on market (EU/AU EMV, US/AU non-EMV, Canada EMV, Canada non-EMV).

EMV & Contactless

Attr #	Name	Default	Purpose
4359	EMV Contactless Transaction Limit	-	Maximum transaction amount approvable via contactless EMV. Above this, chip insertion is required. Set to 0 to remove the limit.
313	Transaction Start Ignore List	Ignore None	Controls which card types are blocked from starting a transaction before product selection.

SME flag: Attr 584 cross-reference (PIP-1114)

This article references Attr 584 (Default Credit) in relation to Attr 4359. PIP-1114 flags that auValue in DTM transaction reports may be populated from Attr 584's setting rather than the actual transaction value. Verify with Tier 2 whether this is fixed or still open before publishing to the master reference.

VPOS Settings

The following three attributes are visible in the Nayax Core UI, but their full value enumerations are not yet documented. Screenshot values are shown for reference.

Attr #	Name	Default	Purpose
-	VPOS Button Function	5 - Btn Start/Card Start + External Cancel (screenshot)	Controls behaviour of the VPOS physical button and its interaction with card start/cancel events.
-	VPOS Card Options	Track2 Only (screenshot)	Defines which card data tracks the VPOS reads during a transaction.
-	VPOS Read Source Enabled	All Read Sources Enabled (screenshot default)	Specifies which physical read sources (contactless, chip, swipe) are active.

SME flag: VPOS Button/Card attributes

Full value enumerations for VPOS Button Function, VPOS Card Options, and VPOS Read Source Enabled are not documented. Contact the VPOS PM for current spec before this content moves into the master attribute reference (PROP-84).

2. Payment

Configures payment-related parameters, including the credit given to the VMC, product selection timeout, EMV price source, special payment modes, and Prepaid revalue limits.

Core Payment Settings

Attr #	Name	Default	Purpose
-	Card Enabled	Checked (enabled)	Enables or disables card payment acceptance. Uncheck for cash-only mode.
584	Default Credit	300 (screenshot value)	Amount of credit sent to the VMC to allow product selection. Also used as the authorisation amount in the pre-auth flow. Format must match Decimal Place (Attr 523). Must be lower than Attr 4359.
617	Choose Product Timeout (sec)	40 (screenshot value)	Time the customer has to select a product after credit is provided before the transaction is cancelled.

EMV Price Table

Determines the source of product prices when an EMV credit card is used. Optionally adds a surcharge.

Syntax	Behaviour	Example result
@$	Use server price (product map in Nayax Core)	Product map = $2.50, charged $2.50
C%100	Use the machine price, no surcharge	Machine = $2.00, charged $2.00
C%NNN	Machine price + percent surcharge	C%110 = +10%. Machine $2.00, charged $2.20
C+NNN	Machine price + fixed amount	C+50 = +50 cents. Machine $2.00, charged $2.50
C+0	Machine price, no surcharge (screenshot default)	Equivalent to C%100

Payment Flags

Screenshot value	Behaviour
Allow Pre-Selection on Pre-Paid cards	Enables pre-selection mode for Prepaid cardholders. The customer selects a product before the payment session starts.

See Payment attribute panel screenshot above.

Multivend Settings

Attr #	Name	Default	Purpose
-	Multivend	Multivend Disabled (screenshot default)	Allows multiple product selections in a single payment session without re-presenting a card for each purchase.
-	False Multivend	False Multivend Disabled (screenshot default)	Configures behaviour when the VMC reports a successful vend but no product was dispensed.

3. MDB

Defines the MDB (Multi-Drop Bus) protocol settings governing communication between the Nayax device and the Vending Machine Controller (VMC), including cashless addressing, transaction mode, communication timing, and timeout values.

Core MDB Settings

Attr #	Name	Default	Purpose
98	Cashless MDB Address	-	Defines the unit's MDB cashless device address used when communicating with the VMC.
621	MDB Flags	02 PreSelection Enabled (screenshot value)	Changes the MDB standard behaviour. Configures preauthorization or preselection mode.
-	Ignore VMC Configuration	Checked (enabled, screenshot default)	When enabled, the device ignores the VMC's MDB configuration handshake and uses its own stored settings.
-	Ignore Start State	Unchecked (disabled)	When enabled, the device ignores the MDB Start State signal from the VMC.
-	MDB Level 3 Optional Features	-	Defines optional MDB Level 3 features. Only applicable when Card Reader MDB Level (Attr 520) is set to 3.

Transaction Behaviour

Attr #	Name	Default	Purpose
-	MDB Communication Time Delay (ms)	-	Delay between the device powering up and the start of MDB communication. Increase for machines needing extra warm-up time.
-	Disable Sending Cash Sale Notification	Unchecked (disabled)	Prevents the device from sending cash transaction reports to the Nayax server.
-	Post Cash Sale Timeout	0 (screenshot default)	Wait time after a cash sale before the device returns to idle.

Timeout Settings

Attr #	Name	Default	Purpose
-	Vend Result Timeout (max 65,535 sec)	40 seconds	How long the device waits for a Vend Success/Failure from the VMC after authorisation. Increase for slow-dispensing machines.
-	Reader State Error Event Timeout (max 255 sec)	90 (screenshot value)	How long the device waits before sending a Reader State Error alert. Set to 0 to disable.
-	MDB Rx Timeout (sec)	60 (screenshot value)	How long the device waits for a complete MDB response before treating communication as failed.
-	Poll IRQ Timeout (ms)	500 (screenshot value)	Timeout for MDB poll interrupt requests.
-	Poll Stop Event Timeout (sec)	90 (screenshot value)	Time the device waits after a poll stop event before taking further action.
-	Session Complete Timeout (ms)	500 (screenshot value)	Time the device waits for the VMC to confirm session completion after a vend.

4. Communication

Defines how the device connects to the Nayax network via APN (SIM), VPN, or MQTT, and configures the server addresses and keep-alive interval used to maintain that connection.

Communication Mode

Value	Behaviour
Disabled (Default)	Connects using APN with a dynamic IP address (SIM-based). Standard mode for most deployments.
VPN Enabled	Connects via VPN with a static IP. If VPN fails, automatically falls back to APN.
MQTT Enabled	Connects via APN with the MQTT protocol. MQTT configuration is pushed automatically.
VPN Only	Connects via VPN only, no APN fallback. If VPN fails, the device goes offline.

Connectivity Parameters

Attr #	Name	Default	Purpose
-	Keep Alive Poll Interval (sec)	2500 seconds (~41 min)	How frequently the device pings the Nayax server to confirm it is online. Reducing this increases SIM data usage.
-	GPRS Data Volume Request	Reset Data Counter (screenshot value)	Controls GPRS data volume tracking or counter reset behaviour.
-	WPN Primary Address	-	Primary APN server address. First address attempted when using APN.
-	WPN Backup Address	-	Backup APN server address. Attempted if primary fails.
-	VPN Primary Address	-	Primary VPN server address. First address attempted.
-	VPN Secondary Address	-	Secondary VPN server address. Attempted if primary fails.
-	VPN Backup Address	-	Backup VPN server address. Attempted if primary and secondary fail.

5. DEX/DDCMP

Configures DEX (Data Exchange) reads from the vending machine, including the read schedule, DEX protocol type, retry settings, CRC validation method, and offline alert scanning.

DEX Reads Schedule

Syntax	Behaviour	Example
HHMM,HHMM,...	Fixed reads at the listed 24h times. Up to 12 entries, comma-separated.	1200,1400,1600,2200
@NNN	Read at a fixed interval in minutes (3-digit zero-padded).	@060 = every 60 minutes
@$	Cancel the DEX read schedule.	-

DEX Type

Value	Use case
DEX/UCS (Default)	Standard DEX protocol. Suitable for the majority of vending machines.
DDCMP RS232	For specific deployments requiring DDCMP over RS232. Default baud rate: 9600.
VCCS Printer	For China Fuji vending machines.
Rhea machine	For Romania Delmaier deployments.

Retry & CRC Settings

Attr #	Name	Default	Purpose
-	DEX Read Retry Counter	0 (no retries)	Number of times the device retries a DEX read after a failed attempt. Increase for intermittent connection issues.
-	Dex Read Retry Period (sec)	0 seconds	Wait time between retry attempts. Only relevant when DEX Read Retry Counter is greater than 0.
-	Dex/DDCMP CRC16 Methode	Ignore bytes with value less 20H	Controls CRC16 checksum validation. Excludes control characters below 0x20 from the calculation.

Offline DEX Alerts

Attr #	Name	Default	Purpose
-	Offline Dex Alerts Read Interval (sec)	0 (scanning disabled)	How frequently the device scans the DEX stream for alert strings when offline. Set non-zero to enable.
-	Offline Dex Alerts Read Timeout (sec)	15 seconds	Maximum time to wait for a DEX read response during an offline alert scan.

6. Device Features

Customises the behaviour of the device's physical buttons, manages data consumption, and provides access to diagnostic tools. Also surfaces read-only hardware and firmware information.

Button Configuration

The device has two physical buttons, BT1 (Red) and BT2 (Yellow). Each supports a short press (under 2 sec) and long press (over 2 sec), giving four configurable actions.

Button	Press type	Screenshot value
BT1 Red button	Long (>2 sec)	Full Machine + Cash + DEX
BT1 Red button	Short (<2 sec)	Pick + DEX
BT2 Yellow button	Long (>2 sec)	Counter Request
BT2 Yellow button	Short (<2 sec)	Full Machine + DEX

Data & Diagnostics

Attr #	Name	Default	Purpose
-	Data Reduction	179 Delta DEX + Poll Delay + No DEX + LCD R... (screenshot, truncated)	Reduces the device's data consumption by disabling or limiting specific data-intensive functions. Use on metered SIM connections.
-	Gtrace Request	Dump 60k records from Flash Gtrace (screenshot value)	Requests a Gtrace diagnostic log from the device, capturing detailed event and communication data from flash memory.
-	Door Open Default State	0 (screenshot value)	Defines the door sensor's default state.

Read-Only Device Information

These fields are populated automatically by the device and cannot be edited. They do not have a checkbox in the Nayax Core UI.

Field	Description
Device PCB Revision (Read Only)	Hardware revision of the device's printed circuit board. Useful for hardware compatibility diagnostics.
Device software version (Read Only)	Firmware version currently running on the device, including release label and build date.
RTC Time Zone (Read Only)	Real-time clock time zone offset set on the device.
SPI Flash 1 Size (Read Only)	Size of the first SPI flash memory module in bytes.
SPI Flash 2 Size (Read Only)	Size of the second SPI flash module, if present. Empty if no second module installed.

7. LCD

Defines the text displayed on the VPOS device's LCD screen, including the welcome message, transactional prompts, and the ability to remove unwanted messages. All messages are limited to 16 characters per row.

Read-Only Status Fields

Field	Description
LCD Status (Read Only)	Error code shown on the LCD when in Cash Only mode. Sent on every keep-alive. Only displayed if the Cash Only message is 16 characters or fewer.
LCD Message (Read Only)	The current message being displayed on the LCD, sent on every keep-alive.

Customisable Messages

Type @$ in any field to restore the device's default message for that attribute.

Attr #	Name	Default	Purpose
-	Welcome Message	Insert Card or Press Start (screenshot value)	Message displayed when the device is idle. Max 16 characters per row. Supports special tokens.
-	Cash Only Message	Cash Only (screenshot value)	Message displayed when the device is in cash-only mode. Max 16 characters per row.
-	Choose Product Message	-	Message prompting the customer to select a product.
-	Take Product Message	-	Message instructing the customer to collect their product after a successful vend.
-	Remove LCD Message	-	Removes a specific unwanted LCD message from the device display.

Welcome Message - Special Tokens

These tokens insert dynamic content or control display formatting. Supported in the Welcome Message field only.

Token	Behaviour	Notes
%s	Inserts the unit's own CLI (phone) number	Useful for displaying a support number on the idle screen
%m	Inserts the Monyx Machine ID	Supported from firmware 3.0.0.4 and above
\n	Starts a new line on the LCD	Max 16 characters per row
\f	Switches between primary and secondary language	Requires a secondary language configured on the device
\0	Marks end of string; characters after this are ignored	-
@$	Restores the default welcome message	Clears any custom message

8. VMC & Sim Card

Both sections are entirely read-only. They surface identification and diagnostic data about the SIM card installed in the device and the VMC it is connected to. No configuration is possible here.

Sim Card

Field	Description
Sim Serial Number (Read Only)	The ICCID of the SIM installed in the device. Use when reporting connectivity issues to your SIM provider or to Nayax Support.

VMC (Vending Machine Controller)

Field	Description
MDB Level (Read Only)	The MDB level reported by the VMC. Should match Card Reader MDB Level (Attr 520). A mismatch will cause transaction failures.
Manufacturer Code (Read Only)	The VMC manufacturer code reported over MDB. Used for diagnostics and identifying the connected machine brand.
Model Number (Read Only)	Model number of the connected vending machine as reported by the VMC.
Serial Number (Read Only)	Serial number of the connected vending machine. Useful for asset tracking and support escalations.
S/W Revision (Read Only)	Firmware version currently running on the VMC. Use when troubleshooting compatibility issues.

Confirmation