ZBasic System Library
98
ZBasic Microcontrollers
Type
Subroutine
Invocation
DefineBus(port, alePin, rdPin, wrPin)
Parameter
Method
Type
Description
port
ByVal
integral
The port to use for address and data. PortA=0, PortB=1, etc.
alePin
ByVal
integral
The pin to use for the address latch strobe.
rdPin
ByVal
integral
The pin to use for the read data strobe.
wrPin
ByVal
integral
The pin to use for the write data strobe.
Discussion
This subroutine is used to define the parameters to use for subsequent BusRead() and BusWrite()
operations. The port specified by the port parameter is used both for outputting the address from which
to read/write and for reading/writing the data. The port is specified by giving a port index – PortA = 0,
PortB = 1, etc. You may use the built-in constants Port.A, Port.B, etc. to specify the port index. If all
the parameters are valid, the pin specified by the alePin parameter is set to output low while the pins
specified by the rdPin and wrPin parameters are set to output high. If any of the provided parameters
is invalid, the bus will not be properly configured and subsequent calls to BusRead() or BusWrite()
will return immediately with no effect.
The pin numbers specified for the alePin, rdPin and wrPin parameters must all be different and none
of them should be in the port specified by the port parameter. If these conditions are violated, the result
is undefined.
Example
Call DefineBus(Port.A, C.0, C.1, C.2)
Compatibility
This subroutine is not available on ZX models that are based on the ATmega32 processor (e.g. the ZX-
24) nor is is available on ATxmega-based ZBasic devices. Moreover, it is not available in BasicX
compatibility mode.
See Also
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