Intel 87C196CB Manual De Usuario

6-2

Address:

Reset State:

1FACH

C0H

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.

—

—

M1

M0

GO

ACH2

ACH1

ACH0

7:6

—

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

5:4

M1:0

A/D Mode

These bits determine the A/D mode.

0

0

10-bit conversion

0

1

8-bit conversion

1

0

threshold detect high

1

1

threshold detect low

3

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

2:0

ACH2:0

A/D Channel Selection

Write the A/D conversion channel number to these bits. The 87C196CB 
has eight A/D channel inputs, numbered 0–7.

†

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.