History A real-time clock built of TTL chips around 1979 Even after Very-Large-Scale Integration (VLSI) CMOS integrated circuit microprocessors made multiple-chip processors obsolete, TTL devices still found extensive use as glue logic interfacing between more densely integrated components. TTL became the foundation of computers and other digital electronics. Some TTL chips are now also made in surface-mount technology packages. TTL devices were originally made in ceramic and plastic dual in-line package(s) and in flat-pack form. Variations of the original TTL circuit design offered higher speed or lower power dissipation to allow design optimization. TTL manufacturers offered a wide range of logic gates, flip-flops, counters, and other circuits. The 7400 series by Texas Instruments became particularly popular. Īfter their introduction in integrated circuit form in 1963 by Sylvania Electric Products, TTL integrated circuits were manufactured by several semiconductor companies. TTL integrated circuits (ICs) were widely used in applications such as computers, industrial controls, test equipment and instrumentation, consumer electronics, and synthesizers. Its name signifies that transistors perform both the logic function (the first 'transistor') and the amplifying function (the second 'transistor'), as opposed to earlier resistor–transistor logic (RTL) and diode–transistor logic (DTL). Go for dedicated Three state drivers, like 74HC1G126.Transistor–transistor logic ( TTL) is a logic family built from bipolar junction transistors. If you use more than 2 slaves, or if you use high speed SPI, then I don´t recommend the diode circuit. * automatic CS of the STM SPI periferal (faster, less software overhead) I´d rather use the dedicated CS form the STM_SPI module and use an external 74HC138 as DEMUX. I personally avoid the use of two seperate CS by using standard IO.

* a HC(T)1G08 gives better LOW level and better timing BAT54 is good.īAT54A is a double diode in one SOT-23 package. Thus the lower the voltage drop the better your (noise) margin. So if the diode drop is 0.6V then the STM sees a LOW level of 0.6V (in best case)

* forward current must be >= pull up currentīut the diodes (forward drop voltage) increases the LOW level seen by the STM. * reverse voltage must be >= your SPI signal HIGH level * diode in series from isolator2_MISO (C) to STM_MISO (A)ĭiode is relatively uncritical. * diode in series from isolator1_MISO (C) to STM_MISO (A) * pullup at MISO input directly at the STM While the ADCs most probably will three state it´s MISO, the isolator does not three state it´s output.įor the diode solution to work properly you need at least three pull up resistors and two diodes. You are looking for solution as workaround for one board?ĪS long as CS of an SPI slave is inactive: the slave has to three state MISO.

SPI totem pole output