AD5535
Preliminary Technical Data
AD5535 to PIC16C6X/7X
ADSP-2101/
ADSP-2103*
AD5535*
The PIC16C6x/7x 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
SCLK
SCLK
D
DT
IN
TFS
SYNC
(SSPCON). See the PIC16/17 Microcontroller User Manual. In
*ADDITIONAL PINS OMITTED FOR CLARITY
SYNC
this example, I/O port RA1 is being used to pulse
and
enable the serial port of the AD5535. This microcontroller
transfers only eight bits of data during each serial transfer
operation; therefore, three consecutive write operations are
necessary to transmit 19 bits of data. Data is transmitted MSB
first. It is important to left-justify the data in the SPDR register
so that the first 19 bits transmitted contain valid data. RA1 must
be pulled low to start a transfer. It is taken high and pulled low
again before any further write cycles can take place. Figure 13
shows the connection diagram.
Figure 11. AD5535 to ADSP-2101/ADSP-2103 Interface
AD5535 to MC68HC11
The serial peripheral interface (SPI) on the MC68HC11 is
configured for master mode (MSTR = 1), clock polarity bit
(CPOL) = 0, and clock phase bit (CPHA) = 1. The SPI is
configured by writing to the SPI control register (SPCR)—see
the 68HC11 User Manual. SCK of the 68HC11 drives the SCLK
of the AD5535 and the MOSI output drives the serial data line
SYNC
(DIN) of the AD5535. The
line (PC7). When data is being transmitted to the AD5535, the
SYNC
signal is derived from a port
PIC16C6x/7x*
AD5535*
SCLK
SCK/RC3
line is taken low (PC7).
D
SDI/RC4
RA1
IN
SYNC
Data appearing on the MOSI output is valid on the falling edge
of SCK. The 68HC11 transfers only eight bits of data during
each serial transfer operation; therefore, three consecutive write
operations are necessary to transmit 19 bits of data. Data is
transmitted MSB first. It is important to left-justify the data in
the SPDR register so that the first 19 bits transmitted contain
valid data. PC7 must be pulled low to start a transfer. It is taken
high and pulled low again before any further write cycles can
take place. See Figure 12.
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 13. AD5535 to PIC16C6x/7x Interface
AD5535 to 8051
The AD5535 requires a clock synchronized to the serial data.
The 8051 serial interface must, therefore, be operated in
Mode 0. In this mode, serial data exits the 8051 through RxD,
SYNC
and a shift clock is output on TxD. The
signal is derived
from a port line (P1.1). Figure 14 shows how the 8051 is
connected to the AD5535. Because the AD5535 shifts data out
on the rising edge of the shift clock and latches data in on the
falling edge, the shift clock must be inverted. Note also that the
AD5535 requires its data with the MSB first. Because the 8051
outputs the LSB first, the transmit routine must take this into
account.
MC68HC11*
AD5535*
SCLK
SCK
D
MOSI
PC7
IN
SYNC
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 12. AD5535 to MC68HC11 Interface
8051*
AD5535*
SCLK
TxD
RxD
P1.1
D
IN
SYNC
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 14. AD5535 to 8051 Interface
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