Memory Map

Table 27-1. Multiplexed Analog Input Channels

Multiplexed

Channels

Analog Input

 

 

 

ANW

Even numbered channels from 0 to 6

 

 

ANX

Odd numbered channels from 1 to 7

 

 

ANY

Even numbered channels from 16 to 22

 

 

ANZ

Odd numbered channels from 17 to 23

 

 

27.4.6 Voltage Reference Signals

VRH and VRL are the dedicated input signals for the high and low reference voltages. Separating the reference inputs from the power supply signals allows for additional external filtering, which increases reference voltage precision and stability, and subsequently contributes to a higher degree of conversion accuracy.

NOTE

VRH and VRL must be set to VDDA and VSSA potential, respectively. For more information, refer to Section 27.9.

27.4.7 Dedicated Analog Supply Signals

The VDDA and VSSA signals supply power to the analog subsystems of the QADC module. Dedicated power is required to isolate the sensitive analog circuitry from the normal levels of noise present on the digital power supply.

27.4.8 Dedicated Digital I/O Port Supply Signal

VDDH provides 5-V power to the digital I/O functions of QADC port QA and port QB. This allows those signals to tolerate 5 volts when configured as inputs and drive 5 volts when configured as outputs.

27.5 Memory Map

The QADC occupies 1 Kbyte, or 512 half-word (16-bit) entries, of address space. Ten half-word registers are control, port, and status registers, 64 half-word entries are the CCW table, and 64 half-word entries are the result table which occupies 192 half-word address locations because the result data is readable in three data alignment formats. Table 27-2is the QADC memory map.

MOTOROLA

Chapter 27. Queued Analog-to-Digital Converter (QADC)

27-7

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Motorola MCF5281 Voltage Reference Signals, Dedicated Analog Supply Signals, Dedicated Digital I/O Port Supply Signal