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LM12454 Datasheet(PDF) 32 Page - Texas Instruments |
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LM12454 Datasheet(HTML) 32 Page - Texas Instruments |
32 / 45 page ![]() LM12454, LM12458, LM12H458 SNAS079A – MAY 2004 – REVISED FEBRUARY 2006 www.ti.com Bit 10 activates the Test mode that is used only during production testing. Leave this bit reset to “0”. Bit 11 is the Diagnostic bit and is available only in the LM12(H)458. It can be activated by setting it to a “1” (the Test bit must be reset to a “0”). The Diagnostic mode, along with a correctly chosen instruction, allows verification that the LM12(H)458's ADC is performing correctly. When activated, the inverting and non-inverting inputs are connected as shown in Table 6. As an example, an instruction with “001” for both VIN+ and VIN− while using the Diagnostic mode typically results in a full-scale output. 2.3 INTERRUPTS The LM12454 and LM12(H)458 have eight possible interrupts, all with the same priority. Any of these interrupts will cause a hardware interrupt to appear on the INT pin (31) if they are not masked (by the Interrupt Enable register). The Interrupt Status register is then read to determine which of the eight interrupts has been issued. Table 6. LM12(H)458 Input Multiplexer Channel Configuration Showing Normal Mode and Diagnostic Mode Channel Normal Mode Diagnostic Mode Selection VIN+ VIN− VIN+ VIN− Data 000 IN0 GND VREFOUT GND 001 IN1 IN1 VREF+ VREF− 010 IN2 IN2 IN2 IN2 011 IN3 IN3 IN3 IN3 100 IN4 IN4 IN4 IN4 101 IN5 IN5 IN5 IN5 110 IN6 IN6 IN6 IN6 111 IN7 IN7 IN7 IN7 Table 7. LM12454 Input Multiplexer Channel Configuration Channel Selection Data MUX+ MUX − 000 IN0 GND 001 IN1 IN1 010 IN2 IN2 011 IN3 IN3 1XX OPEN OPEN NOTE: The LM12(H)454 is no longer available. Information shown for reference only. The Interrupt Status register, 1010 (A4–A1, BW = 0) or 1010x (A4–A0, BW = 1) must be cleared by reading it after writing to the Interrupt Enable register. This removes any spurious interrupts on the INT pin generated during an Interrupt Enable register access. Interrupt 0 is generated whenever the analog input voltage on a selected multiplexer channel crosses a limit while the LM12(H)454/8 are operating in the “watchdog” comparison mode. Two sequential comparisons are made when the LM12(H)454/8 are executing a “watchdog” instruction. Depending on the logic state of Bit 9 in the Instruction RAM's second and third sections, an interrupt will be generated either when the input signal's magnitude is greater than or less than the programmable limits. (See the Instruction RAM, Bit 9 description.) The Limit Status register will indicate which preprogrammed limit, #1 or #2 and which instruction was executing when the limit was crossed. Interrupt 1 is generated when the Sequencer reaches the instruction counter value specified in the Interrupt Enable register's bits 8–10. This flag appears before the instruction's execution. Interrupt 2 is activated when the Conversion FIFO holds a number of conversions equal to the programmable value stored in the Interrupt Enable register's Bits 11–15. This value ranges from 0001 to 1111, representing 1 to 31 conversions stored in the FIFO. A user-programmed value of 0000 has no meaning. See Section 3.0 for more FIFO information. 32 Submit Documentation Feedback Copyright © 2004–2006, Texas Instruments Incorporated Product Folder Links: LM12454 LM12458 LM12H458 |
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