Teletext Processing Circuit
The invention relates to a device that comprises a memory circuit with memory cells that use floating gate storage transistors, which are conventionally called non-volatile memory cells. A particular embodiment relates to a teletext circuit. A teletext processing circuit comprising a decoder logic circuit and a memory circuit integrated together in an integrated circuit, the memory circuit comprising memory cells for storing teletext page data, the memory cells comprising floating gate storage transistors to store the teletext page data. The page data from memory is used to control the content of displayed teletext images.
1 . A teletext processing circuit comprising a decoder logic circuit and a memory circuit integrated together in an integrated circuit, the memory circuit comprising memory cells for storing teletext page data, the memory cells comprising floating gate storage transistors to store the teletext page data.
2 . A teletext processing circuit according to claim 1 , comprising a control circuit arranged to refresh the teletext page data for a teletext page in the memory circuit, by writing newly received teletext page data for that teletext page into the memory cells, the control circuit being arranged to compare the newly received teletext page data, or part thereof, with the stored teletext page data for the teletext page or part thereof, the control circuit being arranged to skip writing the newly received page data if no change is detected.
3 . A teletext processing circuit according to claim 2 , wherein the control circuit is arranged to suppress skipping each time after a receiving newly received teletext page data for the teletext page for a predetermined number of times and/or after a predetermined refresh time interval.
4 . A teletext processing circuit according to claim 1 , wherein the control circuit that is arranged to maintain an assignment of respective teletext pages to variably selectable addresses in the memory circuit, the control circuit being arranged to reassign the teletext page to an address in a different memory sector than a memory sector that stores the stored teletext page data and to write the newly received teletext page data to the reassigned address when the newly received teletext page data differs from the stored teletext page data.
5 . A teletext processing circuit according to claim 1 , comprising a control circuit arranged to refresh the teletext page data in the memory using retrieved page data from the memory cells.
6 . A teletext processing circuit according to claim 5 , wherein a refresh rate of said refreshing is less than once per half hour.
7 . A teletext processing circuit according to claim 1 , comprising a control circuit arranged to detect occurrence of a television reception channel and to disable writing of page data into the memory cells until a predetermined time interval has elapsed after the channel change.
8 . A teletext processing circuit according to claim 7 , wherein the control circuit is arranged to enable writing within said predetermined time interval when activation of a teletext mode is detected.
9 . A teletext processing circuit according to claim 1 , comprising a control circuit and wherein the memory cells are organized into sectors, the control circuit being arranged to control simultaneous erasing of all memory cells in a selected sector before writing teletext page data into memory cells in the sector, the sectors having a size that is at least so large that a time needed for erasing one sector and writing an amount of page data that fits into the sector is less than a time needed for receiving that amount of page data.
10 . A teletext processing circuit according to claim 9 comprising an SRAM or DRAM buffer memory, arranged to buffer at least said amount of page data during erasing of the sector.
11 . A teletext processing circuit according to claim 1 , comprising an SRAM or DRAM buffer memory and a control circuit, the control circuit being arranged to identify one or more selected pages, and to keep page data for these one or more identified pages in the buffer memory without writing the one or more identified pages to the memory cells, or at least without writing data for the one or more identified pages to the memory cells after every change in the one or more identified pages.
12 . An integrated circuit for processing a teletext signal, the integrated circuit comprising a decoder logic circuit and a memory circuit integrated together on a same semi-conductor substrate, the memory circuit comprising memory cells for storing teletext page data, the memory cells comprising floating gate storage transistors to store the teletext page data.
13 . An integrated circuit comprising a data processing circuit, a memory circuit and a refresh circuit, the memory circuit comprising memory cells that comprise floating gate transistors, coupled to the data processing circuit for storing data produced by the logic circuit and/or for supplying stored data for processing by the data processing circuit, the refresh circuit being arranged to refresh data in the memory by reading data from the memory cells and writing back the data that has been read back to the memory cells at a same or a different address.
14 . A method of processing teletext page data, the method comprising storing received teletext page data in floating gate storage transistors, retrieving the teletext page data from the floating gate storage transistors and controlling image display with the retrieved the teletext page data.