High Performance Analog Front End InterfacesのトピックBinary and hexadecimal address mismatch for PCAL6524

Binary and hexadecimal address mismatch for PCAL6524

sbah — Wed, 12 Mar 2025 17:47:38 GMT

Hi,

I am running on an issue on the I2C bus addresses for the PCAL6524. The address in binary does not match the address in hexadecimal. i.e: 0100000 should give us 0x20 but it is saying 0x40 in the chip datasheet (p7/70). Can you guys clarify on what is going on?

Re: Binary and hexadecimal address mismatch for PCAL6524

TomasVaverka — Wed, 12 Mar 2025 19:24:19 GMT

Hi,

The address in hexadecimal is actually the full 8-bit write slave address (R/W bit = 0).

PCAL6524 has fix value for A6 – A2 as “01000”, and programmable A1-A0 settings (depending on what is connected to ADDR pin).

If for example ADDR = VSS, then PCAL6524 uses 0x44 (“0100010” + “0”) for I2C write slave address, and 0x45 (“0100010” + “1”) for I2C read slave address.

If for example ADDR = VDD, then PCAL6524 uses 0x46 (“0100011” + “0”) for I2C write slave address, and 0x47 (“0100011” + “1”) for I2C read slave address.

BRs, Tomas

Re: Binary and hexadecimal address mismatch for PCAL6524

sbah — Wed, 12 Mar 2025 19:08:11 GMT

Hi Thomas, thank you for the clarification.

However, there is only one ADDR pin. It does give A1 and A0 bits different values depending on what is connected to it: SCL, SDA, GND and VS.

Re: Binary and hexadecimal address mismatch for PCAL6524

TomasVaverka — Thu, 13 Mar 2025 07:08:12 GMT

Hi,

Yes, A1 and A0 are not HW address pins, which is quite common in other devices, but 2 bits whose value depends on the connection of the ADDR pin as shown in Table 4.

BR, Tomas