HMS87C5216 Datasheet, PDF (73/76 Pages) List of Unclassifed Manufacturers – CMOS SINGLE-CHIP 8-BIT MICROCONTROLLER FOR UR(Universal Remocon) & WIRELESS KEYBOARD

HMS87C5216
19. ANALOG TO DIGITAL CONVERTER
The analog-to-digital converter (A/D) allows conversion of an
analog input signal to a corresponding 8-bit digital value. The A/
D module has eight analog inputs, which are multiplexed into one
sample and hold. The output of the sample and hold is the input
into the converter, which generates the result via successive ap-
proximation.
The analog reference voltage is V_DD. The A/D module has two
registers which are the control register ADMR and A/D result
register ADDR. The ADMR register, shown in Figure 19-2, con-
trols the operation of the A/D converter module. The port pins
can be configure as analog inputs or digital I/O.
To use analog inputs, each port is assigned analog input port by
setting the bit ANSEL[7:0] in RAFUNC register. And selected
the corresponding channel to be converted by setting ADS[2:0].
The processing of conversion is start when the start bit ADST is
set to “1”. After one cycle, it is cleared by hardware. The register
ADCR contains the results of the A/D conversion. When the con-
version is completed, the result is loaded into the ADCR, the A/
D conversion status bit ADSF is set to “1”, and the A/D interrupt
flag ADIF is set. The block diagram of the A/D module is shown
in Figure 19-1. The A/D status bit ADSF is set automatically
when A/D conversion is completed, cleared when A/D conver-
sion is in process. The conversion time takes maximum 30 uS (at
fxin=4 MHz).
R1[7]/AN3
R1[6]/AN2
R1[5]/AN1
R1[4]/AN0
ADAN[1:0]
ADEN
ADEN
ADEN
ADEN
11
Sample & Hold
10
S/H
01
00
Resistor
Ladder
Circuit
A/D Result Register
ADDR(8-bit)
ADDRESS : EDH
RESET VALUE : Undefined
Successive
Approximation
Circuit
ADIF
A/D Interrupt
AVDD
ADEN
Figure 19-1 A/D Converter Block Diagram
SEP. 2004 Ver 1.01