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M27C322-100P6 데이터시트(PDF) 9 Page - STMicroelectronics |
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M27C322-100P6 데이터시트(HTML) 9 Page - STMicroelectronics |
9 / 13 page 9/13 M27C322 PRESTO III Programming Algorithm The PRESTO III Programming Algorithm allows the whole array to be programed with a guaran- teed margin in a typical time of 100 seconds. Pro- gramming with PRESTO III consists of applying a sequence of 50µs program pulses to each word until a correct verify occurs (see Figure 8). During programing and verify operation a MARGIN MODE circuit must be activated to guarantee that each cell is programed with enough margin. No overprogram pulse is applied since the verify in MARGIN MODE provides the necessary margin to each programmed cell. Program Inhibit Programming of multiple M27C322s in parallel with different data is also easily accomplished. Ex- cept for E, all like inputs including GVPP of the par- allel M27C322 may be common. A TTL low level pulse applied to a M27C322's E input and VPP at 12V, will program that M27C322. A high level E in- put inhibits the other M27C322s from being pro- grammed. Program Verify A verify (read) should be performed on the pro- grammed bits to determine that they were correct- ly programmed. The verify is accomplished with Figure 8. Programming Flowchart AI02206 n = 0 Last Addr VERIFY E = 50 µs Pulse ++n = 25 ++ Addr VCC = 6.25V, VPP = 12V FAIL CHECK ALL WORDS 1st: VCC = 6V 2nd: VCC = 4.2V YES NO YES NO YES NO SET MARGIN MODE RESET MARGIN MODE GVPP at VIL. Data should be verified with tELQV af- ter the falling edge of E. On-Board Programming The M27C322 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 M27C322. To activate the ES mode, the programming equipment must force 11.5V to 12.5V on address line A9 of the M27C322, with VPP = VCC = 5V. Two identifier bytes may then be sequenced from the device out- puts by toggling address line A0 from VIL to VIH. All other address lines must be held at VIL during Electronic Signature mode. Byte 0 (A0 = VIL) represents the manufacturer code and byte 1 (A0 = VIH) the device identifier code. For the STMicroelectronics M27C322, these two identifier bytes are given in Table 4 and can be read-out on outputs Q0 to Q7. ERASURE OPERATION (applies to UV EPROM) The erasure characteristics of the M27C322 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 fluo- rescent lighting could erase a typical M27C322 in about 3 years, while it would take approximately 1 week to cause erasure when exposed to direct sunlight. If the M27C322 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 M27C322 window to prevent unintentional era- sure. The recommended erasure procedure for M27C322 is exposure to short wave ultraviolet light which has a wavelength of 2537 Å. The inte- grated 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 approximate- ly 30 to 40 minutes using an ultraviolet lamp with 12000 µW/cm2 power rating. The M27C322 should be placed within 2.5cm (1 inch) of the lamp tubes during the erasure. Some lamps have a filter on their tubes which should be removed before erasure. |
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