Glue logic

For example, the microcontroller (left, here is a 80C51 ) has a multiplexed address and data bus , while the tailed memory (on the right, here an EPROM separate) address and data buses has; In order to be able to connect the two parts, a register ( latch , in the middle of the picture, e.g. 74373 ) is required as glue logic , which takes over part of the address during the addressing phase of the multiplexed bus and uses it during the subsequent access phase for the Holds address bus of memory; the microcontroller controls the latch using the ALE signal (address latch enable)

The English term glue logic (German: “adhesive logic ” in the sense of connection logic ) refers to a relatively simple logic circuit that was designed to connect two initially incompatible hardware components. The glue logic itself has no further use other than connecting the components. A typical example is a circuit ( memory controller ) for interconnecting a microprocessor with DRAM modules; DRAM has a different bus structure than conventional microprocessors and is usually much slower, so the two components cannot be connected directly. Further examples are address decoding, i.e. the generation of chip select signals from the addresses on the address bus, and the (de) multiplexing of bus signals (see figure).

Today glue logic is almost exclusively implemented using programmable logic modules (mostly FPGAs and CPLDs ); In the past, collections of 74xx chips or other simple logic chips were often used as glue logic .