p87c591vfb NXP Semiconductors, p87c591vfb Datasheet - Page 124

• Manufacturer Part Number: p87c591vfb
• Description: Single-chip 8-bit Microcontroller With Can Controller
• Manufacturer: NXP Semiconductors

Philips Semiconductors
19 PORT 1 OPERATION
Port 1 may be used to input up to 6 analog signals ADC.
Unused ADC inputs may be used to input digital inputs.
These inputs have an inherent hysteresis to prevent the
input logic from drawing excessive current from the power
lines when driven by analog signals. Channel to channel
crosstalk (Ct) should be taken into consideration when
both analog and digital signals are simultaneously input to
Port 3 (see Chapter 24 “DC Characteristics”).
20 ANALOG-TO-DIGITAL CONVERTER (ADC)
20.1
For information on the ADC characteristics, refer to
Chapter 24.
2000 Jul 26
10-bit resolution
6 multiplexed analog inputs
Start of a conversion by software or with an external
signal
Conversion time for one 10-bit analog-to-digital
conversion: 25 s @ 12 MHz
Differential non-linearity (DL
Integral non-linearity (IL
Offset error (OS
Gain error (G
Absolute voltage error (A
Channel-to-channel matching (M
Crosstalk between analog inputs (C
100 kHz
Monotonic and no missing codes
Separated analog (V
voltages
Reference voltage special pin: V
Single-chip 8-bit microcontroller with CAN controller
ADC features
e
): 4%
e
2 LSB
SSA
e
) and digital (V
): 2 LSB
e
): 3 LSB
e
1 LSB
ref(p)(A)
ctc
): 1 LSB
t
): < 60 dB at
DD
.
, V
SS
) supply
124
20.2
The analog input circuitry consists of an 6-input analog
multiplexer and a 10-bit, straight binary, successive
approximation ADC. The A/D can also be operated in 8-bit
mode with faster conversion times by setting bit ADC8
(AUXR1.7). The 8-bit result will be contained in the ADCH
register. The analog reference voltage and analog power
supplies are connected via separate input pins. For 10-bit
accuracy, the conversion takes 50 machine cycles, i.e.,
25 s at an oscillator frequency of 12 MHz. For the 8-bit
mode, the conversion takes 24 machine cycles. Input
voltage swing is from 0 V to +5 V. Because the internal
DAC employs a ratiometric potentiometer, there are no
discontinouties in the converter characteristic. Figure 48
shows a functional diagram of the analog input circuitry.
The ADC has the option of either being powered off in Idle
mode for reduced power consumption or being active in
the Idle mode for reducing internal noise during the
conversion. This option is selected by the AIDL bit of
AUXR1 register (AUXR1.6). With the AIDL bit set, the ADC
is active in the Idle mode, and with the AIDL bit cleared,
the ADC is powered off in Idle mode.
ADC functional description
Preliminary Specification
P8xC591