SAA5290A Philips Semiconductors, SAA5290A Datasheet - Page 13

• Manufacturer Part Number: SAA5290A
• Description: Economy teletext and TV microcontrollers
• Manufacturer: Philips Semiconductors

Philips Semiconductors
7.3.7
Up to 4 successive approximation ADCs can be
implemented in software by making use of the on-chip 8-bit
DAC and multiplexed voltage comparator. The software
ADC uses 4 analog inputs which are multiplexed with
P3.0 to P3.3.
Table 9 ADC input channel selection
The control of the ADC is achieved using the Special
Function Registers SAD and SADB.
SAD.CH1 and SAD.CH0 select one of the four inputs to
pass to the comparator. The other comparator input
comes from the DAC, whose value is set by SAD.SAD7
(MSB) to SAD.SAD4 and SADB.SAD3 to SADB.SAD0
(LSB). The setting of the value SAD.SAD7 to SAD.SAD4
1997 Jul 07
Economy teletext and TV microcontrollers
CH1
S
0
0
1
1
OFTWARE
ADC
CH0
0
1
0
1
INPUT PIN
P3.3/ADC3
P3.0/ADC0
P3.1/ADC1
P3.2/ADC2
13
must be performed at least 1 instruction cycle before the
setting of SAD.ST to ensure comparison is made using the
correct SAD.SAD7 to SAD.SAD4 value.
The output of the comparator is SAD.VHI, and is valid after
1 instruction cycle following the setting of SAD.ST to a
logic 1.
handbook, halfpage
P3.0
P3.1
P3.2
P3.3
MULTIPLEXER
CH1, CH0
Fig.4 SAD block diagram.
REF
SAD7 to SAD0
8-BIT DAC
SAA5x9x family
Preliminary specification
ST
REF
C1
1D
MGL115
VH1