D4-450 CPU, requires external 24VDC power. 30.8K words total memory (7.5K flash ladder memory on board or use optional memory cartridge for up to 15.5K ladder (RAM, UVPROM, or EEPROM cartridges available)), RLL/RLLPLUS programming, including support for up to 16 PID loops and floating point math. Built-in communication ports include an RS-232C programming port and auxiliary RS-232C/RS-422 ports. NOTE: If the D4-450 is replacing a CPU in an existing system, and the system has specialty modules with an F4 part number, (CoPros, SDN, etc.) please contact our Technical Services group before ordering. These modules may require an upgrade to operate with the D4-450. (Does not apply to analog modules.)