ZBasic System Library
264
ZBasic Microcontrollers
Type
Function returning Integer
Invocation
RCTime(pin, level)
Parameter
Method
Type
Description
pin
ByVal
Byte
The pin to use.
level
ByVal
Byte
The expected initial logic level of the pin.
Discussion
This function measures how long the specified pin stays at the given logic level after it is made a tri-state
input. The return value has units as shown in the table below by default but this can be changed using
Register.TimerSpeed2. If the maximum time elapses (32,767 units) and the pin has not changed
logic levels, the return value will be zero. If the pin is not at the specified level when called, the routine
returns immediately with a value of 1. The pin will be left in the input tri-state mode.
RCTime Units
Target
I/O Scaling
Resolution
ZX devices running at 14.7456MHz
True
False
1.085 µS
0.542 µS
all other targets
n/a
1/F_TS2
As an example, this function can be used with an external resistor-capacitor circuit to measure the value
of one element when the other one is known. The charge/discharge time depends on the values of R and
C as well as the initial and final voltages. Before calling this routine, you should make the specified pin an
output and set it to the level specified.
Example
Const pin as Byte = 12
Call PutPin(pin, 1) ' make the pin an output high to start charging
Call Delay(1.4e-4) ' delay a bit to allow nearly full charging
i = RCTime(pin, 1) ' measure the time to reach logic zero level
Resource Usage
This routine uses the I/O Timer. If the timer is already in use when this routine is called, it will return
immediately with a zero value. The same is true if the specified pin is invalid.
Task switching is suspended and interrupts are disabled while the charge/discharge time is being
measured. However, RTC ticks are accumulated during the process and the RTC is updated when the
process has completed so that the RTC does not lose time.
Compatibility
In BasicX, the ability to change the resolution using Register.TimerSpeed2 is not supported.
The BasicX implementation will miss RTC ticks if the charge/discharge time is too long.
 |
 |
 |