p87c770 ETC-unknow, p87c770 Datasheet - Page 32

• Manufacturer Part Number: p87c770
• Description: Microcontrollers Ntsc With On-screen Display Closed Caption
• Manufacturer: ETC-unknow

Philips Semiconductors
16 AFT INPUTS (ADC)
The P8xCx70 has 3 ADC channels each with 4-bit resolution. One channel is intended to measure the level of the key
pad signals. This is achieved by comparing the AFT signal with the output of a 4-bit DAC.
The compare time of the AFT is not greater than 8 s at 12 MHz. Adding NOP instructions is recommended in between
the instructions which change the reference voltage or channel and the instructions which read the AFTC register bit.
Ensure that pins 9, 10 and 11 are configured as AFT functions before use (see Chapter 14).
The conversion time (T
where:
1999 Jun 11
T
T
handbook, full pagewidth
AFC
CPU
Microcontrollers for NTSC TVs with On-Screen
Display (OSD) and Closed Caption (CC)
=
=
P1.0/AFT0
P1.1/AFT1
P1.2/AFT2
T
number of instructions to program 4-bit DAC
(SFR address EAH)
Channel selection
CPU
+
8
4 s
AFC
) of an AFT (4-bit output) is calculated as shown below.
AFTH1
SELECTOR
CHANNEL
AFT
AFTH0
Internal bus
Fig.11 AFT block diagram.
AFTL3
3
V ref
AFTL2
32
4-BIT DAC
AFT2E
EN2
instruction cycle time
DERIVATIVE PORT
COMPARATOR
AFTL1
SELECTOR
AFT1E
EN1
EN
AFTL0
AFT0E
EN0
(SFR address EAH)
AFT function enable
(SFR address F4H)
Internal bus
AFTC
P8xCx70 family
(SFR address EAH)
Product specification
MGL596