6/12/2023 0 Comments Packing and unpackingFor example, each signal lever on a dispatcher’s CTC panel requires 2 input lines corresponding to 2 input bits. When we read an input byte from the railroad we need a similar type of procedure to separate the various bits representing the different input devices. That is, we pack the bits representing different software output variables into a whole byte prior to transmitting the byte out to the railroad. What is needed, is a simple procedure whereby we can position the SE(12) bits to use the lower 3 bits of a port while the SW(9) bits are aligned to use the upper 5 bits of a port. Per the above, SE(12) needs 3 lines and SW(9) needs 5 lines. To provide separate or independent control, each LED is wired to a separate output pin. A typical application for this configured signal would be at the facing point end of a turnout leading into a CTC controlled passing siding. Thus SW(9) corresponds to 5 output lines. one line for each of the 3 LEDs.Īdditionally, let’s assume that SW(9) is a two-head 5-LED signal containing green, yellow and red LEDs on the upper head and yellow and red LEDs on the lower head. For example, if SE(12) represents a 3-LED signal at the east end of Block 12, it corresponds to 3 output lines, i.e. However, most software variables within our programs correspond to only a few hardware lines. Neither QuickBASIC nor Visual Basic, nor most other programming languages, read or write at the individual line, or bit level. Software must write to each output card a byte at a time. Software must read from each input card a byte at a time. Software, when it reads and writes to an I/O card’s port, must treat the grouping of the 8-bits for each port as a single entity. Each byte has 8 bits and they exhibit a one-to-one correspondence to the 8 lines for each port. Like the wire itself, each software bit can assume two states typically referred to as being either high or low, on or off, 1 or 0, etc. The software needs to be able to look at each of the wired-lines on each port as a bit. This way the software monitors the status of devices on the railroad. With an input card we read the value that the railroad has set on each line. ![]() This way the software controls devices on the railroad. Using an output card, we write to, or set, the values on each output line. Eight bits, when grouped together as they are within each port, are referred to as a “byte.” Therefore, each port is equivalent to 1 byte (of data), made up of 8 individual bits. In computer-ese we often speak of an I/O line as a “binary bit” or simply “bit” for short. Each line within a port has two states typically referred to as being either high or low, on or off, 1 or 0, +5Vdc or 0 and so forth. The ports are labeled A, B and C for 24-line cards and A, B, C and D for 32-line cards. These cards can be the separate cards plugged into an I/O motherboard or the “I/O cards” built into the SMINI.Įach I/O card type, input or output, supports either 24- or 32-I/O lines that are grouped together in sets of eight lines each. ![]() Fundamentally, with the C/MRI we always “talk” to the railroad through the I/O cards. This is the packing and unpacking of I/O bytes. Send us feedback about these examples.Click HERE to download a printable copy of Chapter 8 USER'S MANUAL V3.1: CHAPTER 8 Packing and Unpacking I/O Bytesīefore we proceed with more involved application examples, it is important that we explore one area of software where a little further explanation is required before the procedures become clear. These examples are programmatically compiled from various online sources to illustrate current usage of the word 'unpack.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. ![]() Patrick Horan, National Review, 22 Mar. 2023 As the financial world continues trying to unpack what’s happened since the Silicon Valley Bank collapse, the Fed’s decision-making body for monetary policy, the Federal Open Market Committee (FOMC), has decided to again raise its target interest rate. ![]() 2023 However small, unpack your existing confidence in those specific areas. 2023 There are a lot of options to unpack. 2023 But there are a lot of details to unpack. 2023 The Chicago White Sox were in town long enough to unpack, get a nice meal, serve up 13 home runs to the San Francisco Giants, give infielder Hanser Alberto two relief appearances and lose two games in embarrassing fashion in front of their fans. Recent Examples on the Web And there are a lot of dumb jokes to unpack.
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