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TSC80C51C-L20MF Datasheet(PDF) 7 Page - TEMIC Semiconductors |
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TSC80C51C-L20MF Datasheet(HTML) 7 Page - TEMIC Semiconductors |
7 / 19 page TSC80C31/80C51 Rev. E (14 Jan.97) 7 MATRA MHS When the port latch contains a 0, all pFETS in Figure 4. are off while the nFET is turned on. When the port latch makes a 0-to-1 transition, the nFET turns off. The strong pFET, T1, turns on for two oscillator periods, pulling the output high very rapidly. As the output line is drawn high, pFET T3 turns on through the inverter to supply the IOH source current. This inverter and T form a latch which holds the 1 and is supported by T2. When Port 2 is used as an address port, for access to external program of data memory, any address bit that contains a 1 will have his strong pullup turned on for the entire duration of the external memory access. When an I/O pin son Ports 1, 2, or 3 is used as an input, the user should be aware that the external circuit must sink current during the logical 1-to-0 transition. The maximum sink current is specified as ITL under the D.C. Specifications. When the input goes below approximately 2 V, T3 turns off to save ICC current. Note, when returning to a logical 1, T2 is the only internal pullup that is on. This will result in a slow rise time if the user’s circuit does not force the input line high. Oscillator Characteristics XTAL1 and XTAL2 are the input and output respectively, of an inverting amplifier which is configured for use as an on-chip oscillator, as shown in Figure 5. Either a quartz crystal or ceramic resonator may be used. Figure 5. Crystal Oscillator. To drive the device from an external clock source, XTAL1 should be driven while XTAL2 is left unconnected as shown in Figure 6. There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum high and low times specified on the Data Sheet must be observed. Figure 6. External Drive Configuration. TSC80C51 with Secret ROM TEMIC offers TSC80C31/80C51 with the encrypted secret ROM option to secure the ROM code contained in the TSC80C31/80C51 microcontrollers. The clear reading of the program contained in the ROM is made impossible due to an encryption through several random keys implemented during the manufacturing process. The keys used to do such encryption are selected randomwise and are definitely different from one microcontroller to another. This encryption is activated during the following phases : – Everytime a byte is addressed during a verify of the ROM content, a byte of the encryption array is selected. – MOVC instructions executed from external program memory are disabled when fetching code bytes from internal memory. – EA is sampled and latched on reset, thus all state modification are disabled. For further information please refer to the application note (ANM053) available upon request. |
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