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HY29F040AC-55 Datasheet(PDF) 6 Page - Hynix Semiconductor |
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HY29F040AC-55 Datasheet(HTML) 6 Page - Hynix Semiconductor |
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6 / 40 page  6 HY29F040A Output Disable Mode With the /OE input at a logic high level (V IH), output from the device is disabled. This will cause the output pins to be in a high impedance state. It is shown in Table 1 that /CE = V IL and /WE = VIH for Output Disable. This is to differentiate Output Dis- able mode from Write mode and to prevent inadvertant writes during Output Disable. Write Mode Device programming and erase are accomplished via the command register. The contents of the reg- ister serve as inputs to the internal state machine. Outputs of the state machine dictate the function of the device. The command register itself does not occupy any addressable memory locations. The register is a latch used to store the commands along with the addresses and data information needed to execute the command. The command register is written by bringing /WE to V IL, while /CE is at VIL and /OE is at V IH. Addresses are latched on the falling edge of /WE or /CE, whichever happens later, while data is latched on the rising edge of /WE or /CE, which- ever happens first. Standard microprocessor write timings are used. Refer to AC Characteris- tics for Programming/Erase and their respective Timing Waveforms for specific timing parameters. Enable Sector Protect and Verify Sector Protect Modes The HY29F040A has a hardware Sector Protect mode that disables both Programming and Erase operation to protected sectors. In this device there are 8 sectors of 64K bytes each. The sector protect feature is enabled using programming equipment at the user’s site. The device is shipped from Hyundai’s factory with all sectors unprotected. To activate the Sector Protect mode, the user must force V ID on address pin A9 and control pin / OE. The sector addresses (A18, A17 and A16) should be set to the sector to be protected (see Table 3 for the sector address for each of the eight individual sectors). Programming of the protec- tion circuitry starts on the falling edge of /WE pulse and is terminated with the rising edge of /WE. Sector addresses must be held fixed during the /WE pulse. To verify programming of the protection circuitry, the programming equipment must force V ID on the address pin A9 with /CE and /OE at V IL and /WE at V IH. As shown in Table 2, scanning the sector addresses (A18, A17 and A16) while (A6, A1 and A0) = (0, 1, 0) will produce a 01H code at the device output pins for a protected sector. In the Verify Sector Protect mode, the device will read 00H for an unprotected sector. In this mode, the lower order addresses, except for A0, A1 and A6, are don’t care. Address locations with A1 = V IL are reserved for electronic ID manufacturer and de- vice codes. It is also possible to determine if a sector is protected in-system by writing the Elec- tronic ID command (described in the Electronic ID command section below). |
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Similar Description - HY29F040AC-55 |
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