The Siemens 6ES7964-2AA01-0AB0 is the IF964-DP interface module for the SIMATIC S7-400 rack. It functions as a PROFIBUS DP master by default, with the ability to also operate as a DP slave, handling PG/OP communication and direct data exchange (slave-to-slave). It carries a 256 kbyte buffer memory implemented as Dual Port RAM, enough to buffer process data for coordinated multi-drop lines. The module supports SYNC/FREEZE and equidistance modes, which matter when you need deterministic scan cycles across DP slaves. Maximum transmission rate hits 12 Mbit/s, but cable length depends on baud rate — at 9.6 kbit/s you can run 1 200 m, at 12 Mbit/s it drops to 100 m. Plan your segment lengths accordingly.
Panel fit and power budget
It draws up to 450 mA from the backplane bus and dissipates 2 W typical. That's within the S7-400 power budget for most configurations, but check your CPU's total backplane current limit if the rack is heavily loaded. I/O mapping supports up to 244 bytes each for inputs and outputs, with a maximum of 125 DP slaves depending on the CPU used. One slot each is reserved for PG and OP communication.
The description explicitly marks it as a replacement part for the S7-400 DP master function. If you are maintaining an existing S7-400 installation, this is the correct drop-in module for the IF964-DP slot.