5. Input, math and logic blocks

#How to read the block sheets

Each block has a sheet with the same lines, in the same order. This chapter covers 11 blocks: those that bring a number into the function, those that do calculations, those that choose, those that limit and those that keep the previous result.

In the new block menu (right-click the graph, the drawing of the function), the blocks are in four categories: Inputs, Outputs, Tables and Logics. Fixed value and VCU value are in Inputs. The other nine blocks in this chapter are in Logics. This guide divides the Logics into groups (math and logic, selection, limits and state) only to make reading easier: the menu has no such groups. When you hover over a block in the menu, the right-hand column shows its help text. When the help text on the screen describes the block differently, this guide's description prevails.

A block has a title (the name you gave it and, in smaller letters, the type), input sockets on the left, output sockets on the right, and parameters in the body. A socket is the point where a link connects. Next to each socket, the screen shows the name and the current value, with 6 decimal places, calculated by FuelTech Vision on the computer. The gear in the title opens Block settings.

Unconnected input is an input socket with no link. It is 0, not the last value it had. The editor does not warn when an input has no link. There are exceptions, described in the sheets: the Min and Max sockets of the Limiter and the Upper limit and Lower limit sockets of the Hysteresis use the block parameter instead, and the Set value of the SR Latch is 1.

Every link carries a decimal number. A logic signal is the number 1 (true) or 0 (false). What counts as true depends on the block. In the Logic block, an input is true when it is greater than 0: 0, negative numbers and an unconnected input are false, and 0.3 is already true. In the SR Latch, Set and Reset become active when they exceed the block's own Threshold (default 0.5).

The end of each sheet says how much the block takes from two VCU memories, shared among all the enabled functions in the map. The working memory (limit of 512 bytes) stores what the block calculates in each cycle: the output and, in some blocks, a state. The configuration memory (limit of 2048 bytes) stores the block type, the connections and the parameters. The editor's memory meter shows both, in the RAM and Settings bars. Blocks with state (Hysteresis, SR Latch and Band multiplexer) restart from zero every time a map is written to the VCU.

#Inputs

#Fixed value

Always delivers the same number, which you type in the block.

The output is the number typed, on every execution of the function. The number has about 7 significant digits. Each constant takes memory, and one output can feed several inputs: reuse the same Fixed value instead of repeating the constant.

Memory: 4 bytes of working memory (map limit of 512) and 6 bytes of configuration (limit of 2048).

#VCU value

Reads a channel that the VCU maintains (a sensor reading, a calculated value, a state, data coming from CAN or written by a Value for VCU block) and delivers the number on the link.

The flag channels (on or off) only deliver 0 or 1. If the list ends in an item with no name or called Math channel, do not choose it: it is not a VCU channel and reads 0.

Eight channels appear in the list, but the custom function cannot read them: the value is always 0. They are Processor temperature, VCU Time, VCU Date, VCU Time (the second channel has the same name), Odometer, Trip odometer, Hourmeter and Trip hourmeter. On the FT470, the inputs Analog input #28: Voltage to Analog input #36: Voltage also always read 0.

Unit: the block delivers the number as the VCU stores it, without scale conversion. The FuelTech Vision measurement table declares a base unit per channel, for example MAP (the intake manifold pressure) in bar, temperature in °C and speed in km/h. Check the unit of the channel before comparing the value with a constant: the value stays in the base unit even when the screen shows °F, psi or mph, and the examples in this guide use the base units.

When the measurement comes from a physical input and nothing feeds it, the block shows a warning icon with the text This measure has no input configured in the map. The warning only exists for measurements that come from an input: calculated channels do not generate it.

Memory: 4 bytes of working memory (map limit of 512) and 4 bytes of configuration (limit of 2048).

#Math and logic

#Math operation

Does a calculation with two numbers and delivers the result.

Memory: 4 bytes of working memory (map limit of 512) and 7 bytes of configuration (limit of 2048).

#Logic

Does a logic operation between two inputs and delivers 1 or 0.

Memory: 4 bytes of working memory (map limit of 512) and 7 bytes of configuration (limit of 2048).

#Selection

#Switch

Compares a reference with one or two limits and delivers one of two values.

If the condition is true, the output is the True data; otherwise, it is the False data. The comparisons are strict: at the exact value of the limit the condition is false. There is no hysteresis; for that, use the Hysteresis block. On the screen, the limit socket that the mode does not use is disabled.

Memory: 4 bytes of working memory (map limit of 512) and 13 bytes of configuration (limit of 2048).

#Multiplexer

Chooses one of four input channels by the selector number.

The selector is truncated to an integer: the decimal part is discarded. From 0 to 0.99 it chooses Channel 1; from 1 to 1.99, Channel 2; from 2 to 2.99, Channel 3; from 3 upward, Channel 4. Outside that range there is no error: negative values choose Channel 1. A selector with no link (0) also chooses Channel 1. The block has no parameters and no state.

Memory: 4 bytes of working memory (map limit of 512) and 12 bytes of configuration (limit of 2048).

#Band multiplexer

Chooses one of four channels according to the range of values in which the selector falls.

The block tests the ranges in the order A, B, C, D and stops at the first one that contains the selector (the ends count: Min ≤ selector ≤ Max). The output is the value of the channel of that range, which the block memorizes as the last valid value. If no range matches, the output is 0 or the memorized value, according to No match. The memorized value starts at 0 and is what the channel was worth when the range matched: if the channel changes later, the output does not follow. A range with Min greater than Max is off.

Memory: 8 bytes of working memory (map limit of 512) and 48 bytes of configuration (limit of 2048).

#Limits

#Limiter

Keeps a number between a minimum and a maximum.

If the input is smaller than the minimum, the minimum comes out. Then, if the result is greater than the maximum, the maximum comes out. Having a link is what counts, not the value: a Min connected to a source that is 0 limits at 0, and the parameter is ignored.

Memory: 4 bytes of working memory (map limit of 512) and 16 bytes of configuration (limit of 2048).

#Deadband

Zeroes the signal while it is inside a range. Outside it, delivers only the part beyond the limit.

input above the upper limit:   output = input − upper limit
input below the lower limit:   output = input − lower limit
input inside the range (includes the limits):  output = 0

With the default range, from −1 to 1: input 3 gives output 2, input −4 gives output −3 and input 0.7 gives output 0.

Memory: 4 bytes of working memory (map limit of 512) and 12 bytes of configuration (limit of 2048).

#State

#Hysteresis

Turns an output on when the signal rises to a limit and turns it off only when it falls to a lower limit.

Input greater than or equal to the upper limit: the output goes to 1. Input smaller than or equal to the lower limit: the output goes to 0. Between the two, the output keeps the previous value. At the exact limits the output also changes.

Memory: 8 bytes of working memory (map limit of 512) and 16 bytes of configuration (limit of 2048).

#SR Latch

Stores a value: a pulse on Set writes it, a pulse on Reset zeroes it, and the value stays stored between the pulses.

• Only Set active: Q = Set value. While Set stays active, Q follows the Set value; when Set drops, Q freezes at the last value.
• Only Reset active: Q = 0.
• Both active: with Reset priority, Q = 0; with Set priority, Q = Set value.
• Neither active: Q keeps the previous value.

Q bar is the Set value when Q is 0 and is 0 when Q is different from 0: only with the Set value at 1 is it the inverse of Q, and with the Set value at 0 both are 0. Q starts at 0 when the VCU is powered on and at every map write; on the first execution, Q bar becomes the Set value. To store a signal of 0 and 1, leave the Set value without a link: it is 1.

Memory: 8 bytes of working memory (map limit of 512) and 16 bytes of configuration (limit of 2048).