programmable devices

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programmable devices
1. Devices under the control of a stored program obeyed by a fetch-execute cycle. See computer, central processor.

2. Integrated circuits whose action is determined by the user either until reprogrammed (erasable programmable devices) or for the life of the device (nonerasable programmable devices). Erasable devices are usually implemented by the storage of static electric charges, whereas nonerasable devices either employ fusible links or have their structure determined at the final masking stage of manufacture.

Static charge or fusible-link devices are called field-programmable, since they may be programmed by the user “in the field”, i.e. on the customer's premises; masked devices are called mask-programmable, implying programmability only at the time of manufacture. This terminology is common for programmed logic. In the case of read-only memory the same distinction often appears as “programmable” (PROM) and, by implication, as “nonprogrammable” (ROM).

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