The usual problem when selecting a microcontroller, once basic performance and architecture issues have been resolved, is to identify a device with the required set of peripherals, and sufficient available IO pins. Almost inevitably, this involves a tradeoff - either a part with extra, unwanted functions has to be used, or extra software effort is required to make up for missing hardware support. When large numbers IO pins are required, it may be necessary to add external IO expansion circuitry.
One possible solution is to implement a processor and the required peripheral set and IOs in an FPGA - but this requires a significant investment in tools, training and possibly also the IP of the processor "core." It is an expensive way of deploying a standard processor architecture when really it is only the peripheral set that needs to be customised. The issues of integrating the processor "core" into the chosen FPGA technology, interfacing to the custom peripherals and debugging the overall design may be non-trivial.
The E5 family bridges the gap between using entirely standard parts, and a fully customised design by integrating an 8051 processor, a memory interface, IO, SRAM, and an area of configurable configurable logic onto a single chip. All except the configurable logic are fixed in silicon, so the designer does not have to be concerned with their implementation, integration, etc.
Because the 8051 is an established industry-standard processor, it is well supported with proven software development tools and other support.
A library of "soft" modules allows common peripherals (eg, UARTs, PWM, I²C) to be implemented in the configurable logic via a simple drag-and-drop interface without the need for any HDL code (modules can also be imported from external design tools if required)
A Configurable System Interconnect (CSI) bus links everything together with a straightforward "socket" style interface:
For systems requiring more processing power, the A7 family uses an ARM7TDMI™ as the processor core - again, an established industry-standard with widespread support.
The E5 and A7 families were originally produced by Triscend, but were discontinued when Xilinx acquired Triscend.