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M2732A-3F1 データシート(PDF) 3 Page - STMicroelectronics |
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M2732A-3F1 データシート(HTML) 3 Page - STMicroelectronics |
3 / 9 page Programming When delivered, and after each erasure, all bits of the M2732A are in the “1" state. Data is introduced by selectively programming ”0’s" into the desired bit locations. Although only “0’s” will be pro- grammed, both “1’s” and “0’s” can be presented in the data word. The only way to change a “0" to a ”1" is by ultraviolet light erasure. The M2732A is in the programming mode when the GVPP input is at 21V. A 0.1 µF capacitor must be placed across GVPP and ground to suppress spu- rious voltage transients which may damage the device. The data to be programmed is applied, 8 bits in parallel, to the data output pins. The levels required for the address and data inputs are TTL. When the address and data are stable, a 50ms, active low, TTL program pulse is applied to the E input. A program pulse must be applied at each address location to be programmed. Any location can be programmed at any time - either individually, sequentially, or at random. The program pulse has a maximum width of 55ms. The M2732A must not be programmed with a DC signal applied to the E input. Programming of multiple M2732As in parallel with the same data can be easily accomplished due to the simplicity of the programming requirements. Inputs of the paralleled M2732As may be con- nected together when they are programmed with the same data. A low level TTL pulse applied to the E input programs the paralleled 2732As. Program Inhibit Programming of multiple M2732As in parallel with different data is also easily accomplished. Except for E, all like inputs (including GVPP) of the parallel M2732As may be common. A TTL level program pulse applied to a M2732A’s E input with GVPP at 21V will program that M2732A. A high level E input inhibits the other M2732As from being pro- grammed. Program Verify A verify should be performed on the programmed bits to determine that they were correctly pro- grammed. The verify is carried out with GVPP and E at VIL. ERASURE OPERATION The erasure characteristics of the M2732A are 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 certain types of fluorescent lamps have wave- lengths in the 3000-4000 Å range. Research shows that constant exposure to room level fluorescent lighting could erase a typical M2732A in approxi- mately 3 years, while it would take approximately 1 week to cause erasure when exposed to the direct sunlight. If the M2732A is to be exposed to these types of lighting conditions for extended pe- riods of time, it is suggested that opaque labels be put over the M2732A window to prevent uninten- tional erasure. The recommended erasure procedure for the M2732A is exposure to shortwave ultraviolet light which has a wavelength of 2537 Å. The integrated dose (i.e. UV intensity x exposure time) for erasure should be a minimum of 15 W-sec/cm2. The era- sure time with this dosage is approximately 15 to 20 minutes using an ultraviolet lamp with 12000 µW/cm2 power rating. The M2732A should be placed within 2.5 cm of the lamp tubes during erasure. Some lamps have a filter on their tubes which should be removed before erasure. Mode E GVPP VCC Q0 - Q7 Read VIL VIL VCC Data Out Program VIL Pulse VPP VCC Data In Verify VIL VIL VCC Data Out Program Inhibit VIH VPP VCC Hi-Z Standby VIH XVCC Hi-Z Note: X = VIH or VIL. Table 3. Operating Modes 3/9 M2732A |
同様の部品番号 - M2732A-3F1 |
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同様の説明 - M2732A-3F1 |
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