MODBUS_MASK_WRITE_RE(3)

💖 MODBUS_MASK_WRITE_RE(3) 💖

okay so bestie, welcome to the libmodbus Manual page for MODBUS_MASK_WRITE_RE(3). This is the one where we mask a single register. Not mask as in hiding your feelings, mask as in bit-math. 💅

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✨ NAME ✨

modbus_mask_write_register — mask a single register. That's it. That's the name. One register, getting the mask treatment. 🎀

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✨ SYNOPSIS ✨

Here's the signature, no cap:

int modbus_mask_write_register(modbus_t *ctx, int addr, uint16_t and,
       uint16_t or);

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✨ DESCRIPTION ✨

The modbus_mask_write_register() function shall modify the value of the holding register at the address addr of the remote device using this algorithm:

new value = (current value AND 'and') OR ('or' AND (NOT 'and'))

It uses the Modbus function code 0x16 (mask single register). iconic. This is giving bit-mask main character energy, periodt. ✨

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✨ RETURN VALUE ✨

The function shall return 1 if successful. Otherwise it shall return -1 and set errno. ngl, 1 is the slay, -1 is the "check errno bestie" moment. 😭

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✨ SEE ALSO ✨

• modbus_read_registers(3)
• modbus_write_registers(3)

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✨ AUTHORS ✨

• Martijn de Gouw <martijn.de.gouw@prodrive.nl>
• The libmodbus documentation was written by Stéphane Raimbault <stephane.raimbault@gmail.com>

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and that's the whole vibe. This page is from libmodbus v3.1.6, dated 11/17/2025. mwah 💋