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AD7811

2.7 V to 5.5 V, 350 kSPS, 10-Bit 4-/8-Channel Sampling ADCs

Analog Devices 

AD7811/AD7812

It is possible to implement a serial interface using the data ports

on the 8051. This would also allow a full duplex serial transfer

to be implemented. The technique involves “bit banging” an

I/O port (e.g., P1.0) to generate a serial clock and using two

other I/O ports (e.g., P1.1 and P1.2) to shift data in and out—

see Figure 22.

AD7811/AD7812*

SCLK

DOUT

DIN

RFS

TFS

8051*

P1.0

P1.1

P1.2

P1.3

AD7811/AD7812 to ADSP-21xx

The ADSP-21xx family of DSPs are easily interfaced to the

AD7811/AD7812 without the need for extra gluing logic. The

SPORT is operated in normal framing mode. The SPORT

control register should be set up as follows:

TFSW = RFSW = 0, Normal Framing

INVRFS = INVTFS = 0, Active High Frame Signal

DTYPE = 00, Right Justify Data

SLEN = 1001, 10-Bit Data Words

ISCLK = 1, Internal Serial Clock

TFSR = RFSR = 1, Frame Every Word

IRFS = 0, External Framing Signal

ITFS = 1, Internal Framing Signal

The 10-bit data words will be right justified in the 16-bit serial

data registers when using this configuration. Figure 24 shows

the connection diagram.

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 22. Interfacing to the 8051 Using I/O Ports

AD7811/AD7812 to TMS320C5x

The serial interface on the TMS320C5x uses a continuous

serial clock and frame synchronization signals to synchronize

the data transfer operations with peripheral devices like the

AD7811. Frame synchronization inputs have been supplied on

the AD7811/AD7812 to allow easy interfacing with no extra

gluing logic. The serial port of the TMS320C5x is set up to

operate in Burst Mode with internal CLKX (Tx serial clock)

and FSX (Tx frame sync). The Serial Port Control register

(SPC) must have the following setup: F0 = 0, FSM = 1,

MCM = 1 and TXM = 1. The connection diagram is shown

in Figure 23.

AD7811/AD7812*

SCLK

DOUT

DIN

RFS

TFS

TMS320C5x*

CLKX

CLKR

DR

DT

FSX

FSR

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 23. Interfacing to the TMS320C5x

AD7811/AD7812*

SCLK

DOUT

DIN

RFS

TFS

ADSP-21xx*

SCLK

DR

DT

RFS

TFS

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 24. Interfacing to the ADSP-21xx

AD7811/AD7812 to DSP56xxx

The connection diagram in Figure 25 shows how the AD7811

and AD7812 can be connected to the SSI (Synchronous Serial

Interface) of the DSP56xxx family of DSPs from Motorola. The

SSI is operated in Synchronous Mode (SYN bit in CRB =1)

with internally generated 1-bit clock period frame sync for both

Tx and Rx (FSL1 and FSL0 bits in CRB = 1 and 0 respectively).

AD7811/AD7812*

SCLK

DOUT

DIN

RFS

TFS

DSP56xxx*

SCK

SRD

STD

SC2

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 25. Interfacing to the DSP56xxx

REV. CB

–17–

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