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M27C512-12C1 Datasheet(PDF) 7 Page - STMicroelectronics |
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M27C512-12C1 Datasheet(HTML) 7 Page - STMicroelectronics |
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7 / 22 page  7/22 M27C512 tion, a 4.7µF bulk electrolytic capacitor should be used between VCC and VSS for every eight devic- es. The bulk capacitor should be located near the power supply connection point.The purpose of the bulk capacitor is to overcome the voltage drop caused by the inductive effects of PCB traces. Figure 6. Programming Flowchart Programming When delivered (and after each erasure for UV EPROM), all bits of the M27C512 are in the '1' state. Data is introduced by selectively program- ming '0's into the desired bit locations. Although only '0's will be programmed, both '1's and '0's can be present in the data word. The only way to change a '0' to a '1' is by die exposure to ultraviolet light (UV EPROM). The M27C512 is in the pro- gramming mode when VPP input is at 12.75V and E is pulsed to VIL. The data to be programmed is applied to 8 bits in parallel to the data output pins. The levels required for the address and data in- puts are TTL. VCC is specified to be 6.25V ± 0.25V. The M27C512 can use PRESTO IIB Pro- gramming Algorithm that drastically reduces the programming time (typically less than 6 seconds). Nevertheless to achieve compatibility with all pro- gramming equipments, PRESTO Programming Algorithm can be used as well. PRESTO IIB Programming Algorithm PRESTO IIB Programming Algorithm allows the whole array to be programmed with a guaranteed margin, in a typical time of 6.5 seconds. This can be achieved with STMicroelectronics M27C512 due to several design innovations described in the M27C512 datasheet to improve programming effi- ciency and to provide adequate margin for reliabil- ity. Before starting the programming the internal MARGIN MODE circuit is set in order to guarantee that each cell is programmed with enough margin. Then a sequence of 100µs program pulses are ap- plied to each byte until a correct verify occurs. No overprogram pulses are applied since the verify in MARGIN MODE provides the necessary margin. Program Inhibit Programming of multiple M27C512s in parallel with different data is also easily accomplished. Ex- cept for E, all like inputs including GVPP of the par- allel M27C512 may be common. A TTL low level pulse applied to a M27C512's E input, with VPP at 12.75V, will program that M27C512. A high level E input inhibits the other M27C512s 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 G at VIL. Data should be verified with tELQV after the falling edge of E. 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 M27C512. To activate the ES mode, the programming equipment must force 11.5V to 12.5V on address line A9 of the M27C512. 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 man- ufacturer code and byte 1 (A0 = VIH) the device identifier code. For the STMicroelectronics M27C512, these two identifier bytes are given in Table 3. and can be read-out on outputs Q7 to Q0. AI00738B n = 0 Last Addr VERIFY E = 100 µs Pulse ++n = 25 ++ Addr VCC = 6.25V, VPP = 12.75V FAIL CHECK ALL BYTES 1st: VCC = 6V 2nd: VCC = 4.2V YES NO YES NO YES NO SET MARGIN MODE RESET MARGIN MODE |
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