MAC7200 datasheet(841/976 Pages) FREESCALE

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Functional Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

763

33.11.3 Digital Sub-blocks

This subsection describes the functions implemented in the digital part. See the register descriptions for

all details.

This block contains all sub-blocks mentioned in Section 33.11.3.1, “Mode / Timing Control” to

Section 33.11.3.8, “Conversion Control”.

33.11.3.1 Mode / Timing Control

The Timing Control is responsible for handling conversions by deciding which channel is to be converted,

when the conversion should start etc. It is responsible for the command/result transfer and the interrupt

generation.

33.11.3.2 Clock Prescaler

The frequency at which the analog conversion circuit can work is between 0.5 MHz and 12 MHz. A higher

system clock frequency must therefore be divided down to fit within this range. This division is provided

by the Clock Prescaler.

33.11.3.3 Bus Interface / Registers

The Bus interface handles read/write accesses from the MCU to the registers and DMA transfers of

conversion results or commands.

33.11.3.4 Command Word / Result / DMA

This block contains the command word queue which consists of ATDCW, ATDCC and ATDRR. It also

takes care of the DMA requests.

33.11.3.5 SYSTRIG0, SYSTRIG1 / External Trigger Input

Triggers can be used to initiate conversions that allow the synchronization of conversions to the external

environment, rather than relying on software to signal to the ATD module when conversions should take

place. The trigger source can be either from one of the analog inputs (from an external source) or from the

SYSTRIG0 / SYSTRIG1 inputs (trigger signals from counters). In this mode there is no access to the

registers.

The trigger is programmable to be edge or level sensitive with polarity control. In Section 33.10.2.2, “ATD

External Trigger Channel Register (ATDETRIGCH)” and Section 33.10.2.1, “ATD Trigger Control

33.11.3.6 Flags

The flags reflect the current ATD status and can be used to generate interrupts.

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