Datasheet

AD7810
–10–
REV. B
MICROPROCESSOR INTERFACING
The serial interface on the AD7810 allows the parts to be directly
connected to a range of many different microprocessors. This
section explains how to interface the AD7810 with some of the
more common microcontroller serial interface protocols.
AD7810 to PIC16C6x/7x
The PIC16C6x Synchronous Serial Port (SSP) is configured
as an SPI Master with the Clock Polarity Bit = 0. This is done
by writing to the Synchronous Serial Port Control Register
(SSPCON). See PIC16/17 Microcontroller User Manual. Figure
17 shows the hardware connections needed to interface to the
PIC16/PIC17. In this example I/O port RA1 is being used to
pulse CONVST and enable the serial port of the AD7810. This
microcontroller transfers only eight bits of data during each
serial transfer operation, therefore, two consecutive read opera-
tions are needed.
SCLK
D
OUT
SCK/RC3
SDO/RC5
RA1
AD7810*
PIC16C6x/7x*
CONVST
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 17. Interfacing to the PIC16/PIC17
AD7810 to MC68HC11
The Serial Peripheral Interface (SPI) on the MC68HC11 is
configured for Master Mode (MSTR = 0), Clock Polarity Bit
(CPOL) = 0, and the Clock Phase Bit (CPHA) = 1. The SPI is
configured by writing to the SPI Control Register (SPCR)—see
68HC11 User Manual. A connection diagram is shown in
Figure 18.
SCLK
D
OUT
SCLK/PD4
MISO/PD2
PA0
AD7810* MC68HC11*
CONVST
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 18. Interfacing to the MC68HC11
AD7810 to 8051
The AD7810 requires a clock synchronized to the serial data;
therefore, the 8051 serial interface must be operated in Mode
0. In this mode serial data enters and exits through RXD, and a
serial clock is output on TXD (half duplex). Figure 19 shows
how the 8051 is connected to the AD7810. However, because
the AD7810 shifts data out on the rising edge of the serial
clock, the serial clock must be inverted.
SCLK
D
OUT
TXD
RXD
P1.1
AD7810* 8051*
CONVST
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 19. Interfacing to the 8051 Serial Port
It is possible to implement a serial interface using the data ports
on the 8051 (or any microcontroller). This would allow direct
interfacing between the AD7810 and 8051 to be implemented.
The technique involves “bit banging” an I/O port (e.g., P1.0)
to generate a serial clock and using another I/O port (e.g., P1.1)
to read in data, see Figure 20.
SCLK
D
OUT
P1.0
P1.1
P1.2
AD7810* 8051*
CONVST
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 20. Interfacing to the 8051 Using I/O Ports