GP521

The GP521 is a general purpose controller/memory chip intended for use with audio signal path circuits in programmable hearing instruments.

The GP521 uses a flexible communication standard which allows room for future growth in programmable functions for hearing instruments. The communication with the program unit is over a bi-directional serial data link. Error detection circuitry is used to avoid undesired changes in programmed settings.

An information transfer dialogue consists of the address and data for a register sent to the GP521 and the register contents returned by the GP521. The function controlled by an output of the GP521 is defined by the signal path circuit allowing current controlled parameters. The relationship between the GP521 register addresses and the function on the signal path circuit is defined by a data file in the programming unit. With this format, any software developed for the GP521 can be used for future generations of Gennum's controller/memory circuits and audio signal path circuits.

The GP521 uses EEPROM cells as the long term memory element. These cells will retain the stored data when the power supply is disconnected. Each EEPROM cell is combined with a temporary (RAM) memory cell which makes it possible to evaluate various control settings prior to saving them in the long term EEPROM memory.

The GP521 controls the audio signal path circuit using eight Programmable Current Sinks (PCS). Each PCS has 16 programmable settings. The circuit of GP521 can be configured for either 6 or 8 PCS outputs. When used with a single pole single throw switch (SPST) under the 6 PCS configuration , GP521 is possible to design a hearing instrument with two programmed settings (i.e. adjusting a low cut filter for either noisy or quiet background environments). The 8 output configuration may be used for circuits that require more programmable but nonswitchable settings. An external reference current is used for the PCS's so that the PCS outputs can track with the currents in the audio signal path circuit.