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M27W801 Folha de dados(PDF) 10 Page - STMicroelectronics |
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M27W801 Folha de dados(HTML) 10 Page - STMicroelectronics |
10 / 16 page M27W801 10/16 On-Board Programming The M27W801 can be directly programmed in the application circuit. See the relevant Application Note AN620. Electronic Signature The Electronic Signature (ES) mode allows the reading out of a binary code from an EPROM that will identify its manufacturer and type. This mode is intended for use by programming equipment to automatically match the device to be programmed with its corresponding programming algorithm. The ES mode is functional in the 25 °C ± 5°C am- bient temperature range that is required when pro- gramming the M27W801. To activate the ES mode, the programming equipment must force 11.5V to 12.5V on address line A9 of the M27W801. Two identifier bytes may then be se- quenced from the device outputs by toggling ad- dress line A0 from VIL to VIH. All other address lines must be held at VIL during Electronic Signa- ture mode. Byte 0 (A0 = VIL) represents the manufacturer code and byte 1 (A0 = VIH) the device identifier code. For the STMicroelectronics M27W801, these two identifier bytes are given in Table 4 and can be read-out on outputs Q7 to Q0. Note that the M27W801 and M27C801 have the same identifier byte. ERASURE OPERATION (applies to UV EPROM) The erasure characteristics of the M27W801 is such that erasure begins when the cells are ex- posed to light with wavelengths shorter than ap- proximately 4000 Å. It should be noted that sunlight and some type of fluorescent lamps have wavelengths in the 3000-4000 Å range. Research shows that constant exposure to room level fluorescent lighting could erase a typical M27W801 in about 3 years, while it would take ap- proximately 1 week to cause erasure when ex- posed to direct sunlight. If the M27W801 is to be exposed to these types of lighting conditions for extended periods of time, it is suggested that opaque labels be put over the M27W801 window to prevent unintentional erasure. The recommend- ed erasure procedure for the M27W801 is expo- sure to short wave ultraviolet light which has wavelength 2537 Å. The integrated dose (i.e. UV intensity x exposure time) for erasure should be a minimum of 30 W-sec/cm2. The erasure time with this dosage is approximately 30 to 40 minutes us- ing an ultraviolet lamp with 12000 µW/cm2 power rating. The M27W801 should be placed within 2.5 cm (1 inch) of the lamp tubes during the erasure. Some lamps have a filter on their tubes which should be removed before erasure. |
Nº de peça semelhante - M27W801 |
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Descrição semelhante - M27W801 |
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