titus-larsen-titus-1981-apple-interfacing

he minimum value should be in the range of 0 or 1. The maximum
alue should be between 253 and 255. This is what is expected from
n 8-bit device, since it can only generate values between 0 and 255.
tep 4
The ADC0804 chip has a Hag output that can be used to monitor
e status of the converter; that is, busy or ready. This output is a
gic zero when data is ready for the computer, and it is a logic one
hen the converter is performing a conversion. This output is really
e output of a flag circuit, and the flag is reset when the eight data
its are read into the computer. Since the converter can perform
any thousands of conversions in a second, is there any need to
onitor this Hag signal
robably not, since the converter will complete the conversion pross
before the data can be accessed by a BASIC-language program.
Can you suggest some possible uses for the Hag output
e flag could be used for assembly-language A/D converter proamming.
In assembly-language programs, ,the flag could be tested
s an input to an input port, or it could be ' used with the interrupt
on the 6502 microprocessor chip. Since thesei.are high-speed. applications,
it would be useful to monitor the flag ;to determine when the
converter had finished a conversion.
Remove line 20 from your program and run the program. What do
OU find
The data values are the same as those observed when the program
was used with the time delay steps. Thus, the converter is "outrun­
·ng" the BASIC control program.
'
The values displayed on the screen do not represent the actual
voltage that is being measured, but are an 8-bit binary representa-
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