Freescale Semiconductor
28-1
Chapter 28
Queued Analog-to-Digital Converter (QADC)
The queued analog-to-digital converter (QADC) is a 10-bit, unipolar, successive approximation converter.
Up to eight analog input channels can be supported using internal multiplexing. A maximum of 18 input
channels can be supported in the expanded, externally multiplexed mode.
The QADC consists of an analog front-end and a digital control subsystem. The analog section includes
input pins, an analog multiplexer, and sample and hold analog circuits.
The digital control section contains queue control logic to sequence the conversion process and interrupt
generation logic. Also included are the periodic/interval timer, control and status registers, the conversion
command word (CCW) table, random-access memory (RAM), and the result table RAM.
The bus interface unit (BIU) provides access to registers that configure the QADC, control the
analog-to-digital converter and queue mechanism, and present formatted conversion results.
28.1
Features
Features of the QADC module include:
Internal sample and hold
Up to eight analog input channels using internal multiplexing
Up to four external analog multiplexers directly supported
Up to 18 total input channels with internal and external multiplexing
Programmable input sample time for various source impedances
Two conversion command word (CCW) queues with a total of 64 entries for setting conversion
parameters of each A/D conversion
Subqueues possible using pause mechanism
Queue complete and pause interrupts available on both queues
Queue pointers indicating current location for each queue
Automated queue modes initiated by:
— External edge trigger and gated trigger
— Periodic/interval timer, within QADC module (queues 1 and 2)
— Software command
Single scan or continuous scan of queues
64 result registers
Output data readable in three formats:
— Right-justified unsigned
— Left-justified signed
— Left-justified unsigned
Unused analog channels can be used as discrete input/output pins.
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3
