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bit bang: n. Transmission of data on a serial line, when accomplished by rapidly
tweaking a single output bit, in software, at the appropriate times. The
technique is a simple loop with eight OUT and SHIFT instruction pairs for
each byte. Input is more interesting. And full duplex (doing input and
output at the same time) is one way to separate the real hackers from the
wannabees. Bit bang was used on certain early models of Prime computers,
presumably when UARTs were too expensive, and on archaic Z80 micros with a
Zilog PIO but no SIO. In an interesting instance of the cycle
of reincarnation, this technique returned to use in the early
1990s on some RISC architectures because it consumes such an infinitesimal
part of the processor that it actually makes sense not to have a UART.
Compare cycle of reincarnation. Nowadays it's used
to describe I2C, a serial protocol for monitoring motherboard
hardware.
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