MC68HC05JJ6 Datasheet, PDF (105/216 Pages) Freescale Semiconductor, Inc – General Release Specification Microcontrollers

Analog Subsystem
This configuration provides several features:
• Two (2) independent voltage comparators with external access to
both inverting and non-inverting inputs
• One voltage comparator can be connected as a single-slope A/D
and the other connected as a single-voltage comparator. The
possible single-slope A/D connection provides these features:
– A/D conversions can use V_DD or an external voltage as a
reference with software used to calculate ratiometric or
absolute results
– Channel access of up to four inputs via multiplexer control with
independent multiplexer control allowing mixed input
connections
– Access to V_DD and V_SS for calibration
– Divide by 2 to extend input voltage range
– Each comparator can be inverted to calculate input offsets
– Internal sample and hold capacitor
– Direct digital output of comparator 1 to the PB4 pin
Voltages are resolved by measuring the time it takes an external
capacitor to charge up to the level of the unknown input voltage being
measured. The beginning of the A/D conversion time can be started by
these means:
• Output compare from the 16-bit programmable timer
• Timer overflow from the 16-bit programmable timer
• Direct software control via a register bit
The end of the A/D conversion time can be captured by these means:
• Input capture in the 16-bit programmable timer
• Interrupt generated by the comparator output
• Software polling of the comparator output using software loop time
MC68HC05JJ6/MC68HC05JP6 — Rev. 3.2
Freescale Semiconductor
Analog Subsystem
General Release Specification
105