Datasheet

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AD9837

Data Sheet

Rev. A | Page 20 of 28

AD9837 to 80C51/80L51 Interface

Figure 26 shows the serial interface between the AD9837 and

the 80C51/80L51 microcontroller. The microcontroller is oper-

ated in Mode 0 so that TxD of the 80C51/80L51 drives SCLK of

the AD9837, and RxD drives the serial data line, SDATA. The

FSYNC signal is derived from a bit programmable pin on the

port (P3.3 is shown in Figure 26).

When data is to be transmitted to the AD9837, P3.3 is taken low.

The 80C51/80L51 transmits data in 8-bit bytes with only eight

falling SCLK edges occurring in each cycle. To load the remain-

ing eight bits to the AD9837, P3.3 is held low after the first eight

bits are 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 that has the

LSB first. The AD9837 accepts the MSB first (the four MSBs are

the control information, the next four bits are the address, and

the eight LSBs contain the data when writing to a destination

must take this into account and rearrange the bits so that the

MSB is output first.

AD9837

FSYNC

SDATA

SCLK

80C51/80L51

P3.3

RxD

TxD

09070-031

Figure 26. 80C51/80L51 to AD9837 Interface

AD9837 to DSP56002 Interface

Figure 27 shows the interface between the AD9837 and the

DSP56002. The DSP56002 is configured for normal mode asyn-

chronous 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 frames the 16 bits (FSL = 0). The frame sync signal is

available on the SC2 pin, but it must be inverted before it is applied

to the AD9837. The interface to the DSP56000/DSP56001 is

similar to that of the DSP56002.

AD9837

FSYNC

SDATA

SCLK

DSP56002

SC2

STD

SCK

09070-032

Figure 27. DSP56002 to AD9837 Interface