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M28W640ECT Datasheet(PDF) 16 Page - STMicroelectronics |
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M28W640ECT Datasheet(HTML) 16 Page - STMicroelectronics |
16 / 55 page ![]() M28W640ECT, M28W640ECB 16/55 Table 8. Program, Erase Times and Program/Erase Endurance Cycles Note: 1. Typical time to program a Main or Parameter Block using the Double Word Program and the Quadruple Word Program commands respectively. BLOCK LOCKING The M28W640EC features an instant, individual block locking scheme that allows any block to be locked or unlocked with no latency. This locking scheme has three levels of protection. s Lock/Unlock - this first level allows software- only control of block locking. s Lock-Down - this second level requires hardware interaction before locking can be changed. s VPP ≤ VPPLK - the third level offers a complete hardware protection against program and erase on all blocks. The protection status of each block can be set to Locked, Unlocked, and Lock-Down. Table 10, de- fines all of the possible protection states (WP, DQ1, DQ0), and Appendix C, Figure 23, shows a flowchart for the locking operations. Reading a Block’s Lock Status The lock status of every block can be read in the Read Electronic Signature mode of the device. To enter this mode write 90h to the device. Subse- quent reads at the address specified in Table 6, will output the protection status of that block. The lock status is represented by DQ0 and DQ1. DQ0 indicates the Block Lock/Unlock status and is set by the Lock command and cleared by the Unlock command. It is also automatically set when enter- ing Lock-Down. DQ1 indicates the Lock-Down sta- tus and is set by the Lock-Down command. It cannot be cleared by software, only by a hardware reset or power-down. The following sections explain the operation of the locking system. Locked State The default status of all blocks on power-up or af- ter a hardware reset is Locked (states (0,0,1) or (1,0,1)). Locked blocks are fully protected from any program or erase. Any program or erase oper- ations attempted on a locked block will return an error in the Status Register. The Status of a Locked block can be changed to Unlocked or Lock-Down using the appropriate software com- mands. An Unlocked block can be Locked by issu- ing the Lock command. Unlocked State Unlocked blocks (states (0,0,0), (1,0,0) (1,1,0)), can be programmed or erased. All unlocked blocks return to the Locked state after a hardware reset or when the device is powered-down. The status of an unlocked block can be changed to Locked or Locked-Down using the appropriate software commands. A locked block can be un- locked by issuing the Unlock command. Parameter Test Conditions M28W640EC Unit Min Typ Max Word Program VPP = VDD 10 200 µs Double Word Program VPP = 12V ±5% 10 200 µs Quadruple Word Program VPP = 12V ±5% 10 200 µs Main Block Program VPP = 12V ±5% 0.16/0.08 (1) 5s VPP = VDD 0.32 5 s Parameter Block Program VPP = 12V ±5% 0.02/0.01 (1) 4s VPP = VDD 0.04 4 s Main Block Erase VPP = 12V ±5% 110 s VPP = VDD 110 s Parameter Block Erase VPP = 12V ±5% 0.4 10 s VPP = VDD 0.4 10 s Program/Erase Cycles (per Block) 100,000 cycles |
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