9511 

The AM9511A arithmetic processing unit was used to enhance the capability of a wide variety of 8-bit microprocessor systems; it provided 16 and 32-bit fixed-point and 32-bit floating-point arithmetic operations, performed trigonometric and inverse trigonometric functions, and executed a variety of mathematical operations such as square root, logarithm and exponentiation.

Data were transferred to and from the APU via a CPU by using operational programmed I/O, or by a direct memory access device if higher transfer speeds were required. All transfers, including operand, result, status and command information, take place over an 8-bit bidirectional data bus. Operands were pushed onto an internal stack and a command is issued to perform operations on the data in the stack. Results were then available to be retrieved from the stack or additional commands could be entered. Upon completion of each command, the APU issued an end of execution signal; this signal could be used as an interrupt by the CPU to help coordinate program execution.