8XC196MC, MD, MH USER’S MANUAL

AD_COMMAND

Address:

1FACH

 

Reset State:

80H

The A/D command (AD_COMMAND) register selects the A/D channel number to be converted, controls whether the A/D converter starts immediately or with an EPA command, and selects the conversion mode.

7

M1

M0

GO

 

 

 

 

0

ACH3

ACH2

ACH1

ACH0

 

 

 

 

Bit

Bit

 

 

Function

Number

Mnemonic

 

 

 

 

 

 

 

 

7

Reserved; for compatibility with future devices, write zeros to these bits.

 

 

 

 

6:5

M1:0

A/D Mode†

 

 

 

These bits determine the A/D mode.

 

 

M1 M0

Mode

 

 

0

0

10-bit conversion

 

 

0

1

8-bit conversion

 

 

1

0

threshold detect high

 

 

1

1

threshold detect low

 

 

 

4

GO

A/D Conversion Trigger††

 

 

Writing this bit arms the A/D converter. The value that you write to it

 

 

determines at what point a conversion is to start.

 

 

0

= EPA initiates conversion

 

 

1

= start immediately

 

 

 

3:0

ACH3:0

A/D Channel Selection

 

 

Write the A/D conversion channel number to these bits.

 

 

 

 

 

While a threshold-detection mode is selected for an analog input pin, no other conversion can be started. If another value is loaded into AD_COMMAND, the threshold-detection mode is disabled and the new command is executed.

††It is the act of writing to the GO bit, rather than its value, that starts a conversion. Even if the GO bit has the desired value, you must set it again to start a conversion immediately or clear it again to arm it for an EPA-initiated conversion.

Figure 12-5. A/D Command (AD_COMMAND) Register

12.4.5 Enabling the A/D Interrupt

The A/D converter can set the A/D interrupt pending bit when it completes a conversion or when the input voltage crosses the threshold value in the selected direction. To enable the interrupt, set the corresponding mask bit in the interrupt mask register (see Table 12-2 on page 12-2) and exe- cute the EI instruction to globally enable servicing of interrupts. The A/D interrupt can cause the PTS to begin a new conversion. See Chapter 5, “Standard and PTS Interrupts,” for details about interrupts and a description of using the PTS in A/D scan mode.

12-8

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Intel 8XC196MD, 8XC196MH, 8XC196MC manual Enabling the A/D Interrupt, Adcommand, ACH3 ACH2 ACH1 ACH0, M1 M0 Mode