The TL16C550A is a functional upgrade of the TL16C450 asynchronous communications element (ACE). Functionally identical to the TL16C450 on power up (character mode), the TL16C550A can be placed in an alternate mode (FIFO) to relieve the CPU of excessive software overhead. In this mode, internal FIFOs are activated allowing 16 bytes (plus 3 bits of error data per byte in the receiver FIFO) to be stored in both receive and transmit modes. To minimize system overhead and maximize system efficiency, all logic is on the chip. Two of the TL16C450 terminal functions (terminals 24 and 29 on the N package and terminals 27 and 32 on the FN package) have been changed to allow signalling of direct memory address (DMA) transfers.