87C752 Philips Semiconductors, 87C752 Datasheet - Page 10

• Manufacturer Part Number: 87C752
• Description: 80C51 8-bit microcontroller family 2K/64 OTP/ROM/ 5 channel 8 bit A/D/ I2C/ PWM/ low pin count
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Special Function Register Addresses
Special function registers for the 8XC752 are identical to those of
the 80C51, except for the changes listed below:
80C51 special function registers not present in the 8XC752 are
TMOD (89), P2 (A0) and IP (B8). The 80C51 registers TH1, TL1,
SCON, and SBUF are replaced with the 8XC752 registers RTH,
RTL, I2CON, and I2DAT, respectively. Additional special function
registers are I2CFG (D8) and I2STA (FB), ADCON (A0), ADAT (84),
PWM (8E), PWMP (8F), and PWENA (FE). See Table 3.
A/D Converter
The analog input circuitry consists of a 5-input analog multiplexer and
an A to D converter with 8-bit resolution. The conversion takes 40
machine cycles, i.e., 40 s at 12 MHz oscillator frequency. The A/D
converter is controlled using the ADCON control register. Input
channels are selected by the analog multiplexer through ADCON
register bits 0–2.
The 83C752 contains a five-channel multiplexed 8-bit A/D converter.
The conversion requires 40 machine cycles (40 s at 12 MHz
oscillator frequency).
The A/D converter is controlled by the A/D control register, ADCON.
Input channels are selected by the analog multiplexer by bits
ADCON.0 through ADCON.2. The ADCON register is not bit
addressable.
ADCON Register
ADCI
1999 Jul 23
MSB
0
0
1
1
80C51 8-bit microcontroller family
2K/64 OTP/ROM, 5 channel 8 bit A/D, I
X
ADDR2
0
0
0
0
1
ADCS
0
1
0
1
X
ADC not busy, a conversion can be started.
ADC busy, start of a new conversion is blocked.
Conversion completed, start of a new conversion is
blocked.
Not possible.
ENADC
INPUT CHANNEL SELECTION
ADDR1
0
0
1
1
0
Operation
ADCI
ADCS
ADDR0
0
1
0
1
0
AADR2
AADR1
INPUT PIN
P1.0
P1.1
P1.2
P1.3
P1.4
AADR0
2
LSB
C, PWM, low pin count
10
Position
ADCON.5 ENADC Enable A/D function when ENADC = 1. Reset
ADCON.4 ADCI
ADCON.3 ADCS
ADCON.2 AADR2
ADCON.1 AADR1
ADCON.0 AADR0
The completion of the 8-bit ADC conversion is flagged by ADCI in
the ADCON register, and the result is stored in the special function
register ADAT.
An ADC conversion in progress is unaffected by an ADC start. The
result of a completed conversion remains unaffected provided ADCI
remains at a logic 1. While ADCS is a logic 1 or ADCI is a logic 1, a
new ADC START will be blocked and consequently lost. An ADC
conversion in progress is aborted when the idle or power-down
mode is entered. The result of a completed conversion (ADCI = logic
1) remains unaffected when entering the idle mode. See Figure 2 for
an A/D input equivalent circuit.
The analog input pins ADC0-ADC4 may be used as digital inputs
and outputs when the A/D converter is disabled by a 0 in the
ENADC bit in ADCON. When the A/D is enabled, the analog input
channel that is selected by the ADDR2-ADDR0 bits in ADCON
cannot be used as a digital input. Reading the selected A/D channel
as a digital input will always return a 1. The unselected A/D inputs
may always be used as digital inputs. Unselected analog inputs will
be floating and may not be used as digital outputs.
The A/D reference inputs on the 8XC752 are tied together with the
analog supply pins AV
voltage on the A/D cannot be varied separately from the analog
supply pins. AV
connected to a supply voltage between 4.5V and 5.5V. A/D
measurements may be made in the range of 4.5V to 5.5V.
Increasing the voltage on the A/D ground reference above 0V or
reducing the voltage on the positive A/D reference below 4.5V is not
permitted.
Symbol
SS
must be connected to 0V and AV
CC
forces ENADC = 0.
ADC interrupt flag. This flag is set when an
ADC conversion is complete. If IE.6 = 1, an
interrupt is requested when ADCI = 1. The
ADCI flag is cleared when conversion data is
read. This flag is read only.
ADC start. Setting this bit starts an A/D
conversion. Once set, ADCS remains high
throughout the conversion cycle. On
completion of the conversion, it is reset just
before the ADCI interrupt flag is cleared.
ADCS cannot be reset by software. ADCS
should not be used to monitor the A/D
converter status. ADCI should be used for this
purpose.
Analog input select.
Analog input select.
Analog input select. This binary coded
address selects one of the five analog input
port pins of P1 to be input to the converter. It
can only be changed when ADCI and ADCS
are both low. AADR2 is the most significant
bit.
and AV
Function
SS
. This means that the reference
83C752/87C752
Product specification
CC
must be