AD5100

Preliminary Technical Data

Rev. PrJ | Page 26 of 32

Figure 21

– Writing a register address to the Address Pointer Register, then writing data to the selected register

Reading Data from AD5100

When reading data from an AD5100 register there are two

possibilities:

1.

If the AD5100’s Address Pointer Register value is

unknown or not at the desired value, it is first necessary

to set it to the correct value before data can be read from

the desired data register. This is done by performing a

write to the AD5100 as before, but only a value

containing the register address is sent, because data is not

to be written to the register. This is shown in Figure 22. A

read operation is then performed consisting of the serial

bus address,

R/W bit set to ‘1’, followed by the data byte

from the data register. This is shown in Figure 23.

2.

If the address pointer is known to be already at the

desire address, data can be read from the

corresponding data register without first writing to the

Address Pointer Register.

Figure 22. Dummy Write to set proper Address Pointer.

Figure 23. Read Data from the Address Pointer Register.

Table 11 shows the read-back data byte structure. Bits [6:0] contain

the data from the register just read. Bit [7] only has significance

when OTP mode is being used, and should be ignored for normal

read operations. The majority of AD5100’s registers are 4-bits wide,

with only the Status/FDR Register and disable Special Function

Register by 7 bit and 5 bits wide respectively.

Table 11

– Read-Back Data Byte Structure

Bit #

[7]

[6]

[5]

[4]

[3]

[2]

[1]

[0]

Function

OTP Okay

D6

D5

D4

D3

D2

D1

D0

Permanent Setting of AD5100 Registers (OTP Function)

When the user wants to permanently program settings to the

AD5100, the one time program (OTP) function is invoked. To

complete a permanent program cycle for a particular register, the

following sequence should be used:

1.

Set bit [0] in register 0x16 using a normal write operation

2.

Set bit [1] in register 0x16 using a normal write operation

3.

Apply a 6V (200mA) voltage source to the OTP pin. This

provides the current for the programming cycle.

4.

Write the desired permanent data to the register of

choice, using a write operation with the OTP bit set to ‘1’

in the Address Pointer byte.

When the write cycle has been completed, the user should allow

minimum of 30ms for the AD5100 to perform the permanent

setting of the internal register. The user has the opportunity to

check whether the AD5100 programmed correctly by performing a

read cycle, and monitoring the state of bit [7] (OTP Okay).

OTP Okay

= 1 indicates the AD5100 programmed correctly

OTP Okay

= 0 indicates the AD5100 programmed incorrectly

Note:

Read-back of the OTP Okay bit is only available for the read

cycle following immediately after the program cycle. If a write or

read of a different register is done immediately after the program

cycle, then the opportunity for verifying if the programming was

successful will have been missed. Figure 24 shows the

recommended way of performing a program then read-back and

above have already been done).

SDA

FRAME 1

SLAVE ADDRESS BYTE

FRAME 2

READ DATA BYTE

SCL

ACK. BY

AD5100

NO ACK. BY

MASTER

STOP BY

MASTER

START BY

MASTER

0

1

0

1

1

AD0

OTP

OK

D6

D5

D4

D3

D2

D1

D0

R/W

03437-0-037

1

SDA

FRAME 1

SLAVE ADDRESS BYTE

FRAME 2

ADDRESS POINTER BYTE

SCL

ACK. BY

AD5100

ACK. BY

AD5100

STOP BY

MASTER

START BY

MASTER

0

1

0

1

1

AD0 R/W

OTP AP6 AP5 AP4 AP3 AP2 AP1 AP0

03437-0-035

1