
Data Sheet
AD9835
Rev. A | Page 21 of 28
AD9835-TO-68HC11/68L11 INTERFACE
the 68HC11/68L11 microcontroller. The microcontroller is
configured as the master by setting bit MSTR in the SPCR to 1
and, this provides a serial clock on SCK while the MOSI output
drives the serial data line SDATA. Since the microcontroller
does not have a dedicated frame sync pin, the FSYNC signal is
derived from a port line (PC7). The setup conditions for correct
operation of the interface are as follows: the SCK idles high
between write operations (CPOL = 0), data is valid on the SCK
falling edge (CPHA = 1). When data is being transmitted to the
AD9835, the FSYNC line is taken low (PC7). Serial data from
the 68HC11/68L11 is transmitted in 8-bit bytes with only eight
falling clock edges occurring in the transmit cycle. Data is
transmitted MSB first. In order to load data into the
AD9835, PC7
is held low after the first eight bits are transferred and a second
serial write operation is performed to the
AD9835. Only after
the second eight bits have been transferred should FSYNC be
taken high again.
AD9835*
FSYNC
SDATA
SCLK
68HC11/68L11*
PC7
MOSI
SCK
*ADDITIONAL PINS OMITTED FOR CLARITY.
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Figure 27. 68HC11/68L11-to
-AD9835 Interface
AD9835-TO-80C51/80L51 INTERFACE
the 80C51/80L51 microcontroller. The microcontroller is
operated in Mode 0 so that TXD of the 80C51/80L51 drives
SCLK of the
AD9835 while RXD drives the serial data line
SDATA. The FSYNC signal is again derived from a bit
programmable pin on the port (P3.3 being used in the
diagram). When data is to be transmitted to the
AAD9835,
P3.3 is taken low. The 80C51/80L51 transmits data in 8-bit
bytes thus, only eight falling SCLK edges occur in each cycle.
To load the remaining eight bits to the
AD9835, P3.3 is held
low after the first eight bits have been transmitted and a second
write operation is initiated to transmit the second byte of data.
P3.3 is taken high following the completion of the second write
operation. SCLK should idle high between the two write
operations. The 80C51/ 80L51 outputs the serial data in a
format which has the LSB first. The
AD9835 accepts the MSB
first (the 4 MSBs being the control information, the next 4 bits
being the address while the 8 LSBs contain the data when
writing to a destination register). Therefore, the transmit
routine of the 80C51/80L51 must take this into account and
rearrange the bits so that the MSB is output first.
AD9835*
FSYNC
SDATA
SCLK
80C51/80L51*
P3.3
RxD
TxD
*ADDITIONAL PINS OMITTED FOR CLARITY.
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Figure 28. 80C51/80L51 to AD9835 Interface
AD9835-TO-DSP56002 INTERFACE
DSP56002. The DSP56002 is configured for normal mode
asynchronous operation with a gated internal clock (SYN = 0,
GCK = 1, SCKD = 1). The frame sync pin is generated internally
(SC2 = 1), the transfers are 16 bits wide (WL1 = 1, WL0 = 0)
and the frame sync signal will frame the 16 bits (FSL = 0).
The frame sync signal is available on pin SC2 but, it needs to be
inverted before being applied to the
AD9835. The interface to
the DSP56000/DSP56001 is similar to that of the DSP56002.
AD9835*
FSYNC
SDATA
SCLK
DSP56002*
SC2
STD
SCK
*ADDITIONAL PINS OMITTED FOR CLARITY.
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