P87C552 datasheet(22/74 Pages) PHILIPS

22 / 74 page

Philips Semiconductors

Preliminary specification

P87C552

80C51 8-bit microcontroller

8K/256 OTP, 8 channel 10 bit A/D, I2C, PWM,

capture/compare, high I/O, low voltage (2.7V–5.5V), low power

1999 Mar 30

PWM0

fOSC

8-BIT COMPARATOR

8-BIT COUNTER

8-BIT COMPARATOR

PWM1

PRESCALER

1/2

OUTPUT

BUFFER

PWMP

OUTPUT

BUFFER

PWM0

PWM1

SU00956

Figure 18. Functional Diagram of Pulse Width Modulated Outputs

INTERNAL BUS

10-BIT A/D CONVERTER

ANALOG INPUT

MULTIPLEXER

1234567

234567

–

STADC

ANALOG REF.

ANALOG SUPPLY

ANALOG GROUND

ADC0

ADC1

ADC2

ADC3

ADC4

ADC5

ADC6

ADC7

ADCON

ADCH

SU00957

Figure 19. Functional Diagram of Analog Input Circuitry

10-Bit Analog-to-Digital Conversion: Figure 20 shows the

elements of a successive approximation (SA) ADC. The ADC

contains a DAC which converts the contents of a successive

approximation register to a voltage (VDAC) which is compared to

the analog input voltage (Vin). The output of the comparator is fed to

the successive approximation control logic which controls the

successive approximation register. A conversion is initiated by

setting ADCS in the ADCON register. ADCS can be set by software

only or by either hardware or software.

The software only start mode is selected when control bit ADCON.5

(ADEX) = 0. A conversion is then started by setting control bit

ADCON.3 (ADCS). The hardware or software start mode is selected

when ADCON.5 = 1, and a conversion may be started by setting

ADCON.3 as above or by applying a rising edge to external pin

STADC. When a conversion is started by applying a rising edge, a

low level must be applied to STADC for at least one machine cycle

followed by a high level for at least one machine cycle.

P87C552 Datasheet(PDF) 22 Page - NXP Semiconductors

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