© 2018 Integrated Device Technology, Inc.

14

August 22, 2018

F1958 Datasheet

Progra m m ing

Se ria l M ode

shifted in LSB (D0) first. When serial programming is used, all the parallel control input pins (1, 19 - 24) must be grounded.

T a ble 8 .

7 -Bit SPI Word Se que nc e

Data Bit

Symbol

D7

Not Used

D6

Attenuation 16 dB Control Bit

D5

Attenuation 8 dB Control Bit

D4

Attenuation 4 dB Control Bit

D3

Attenuation 2 dB Control Bit

D2

Attenuation 1 dB Control Bit

D1

Attenuation 0.5 dB Control Bit

D0

Attenuation 0.25 dB Control Bit

T a ble 9 .

T rut h T a ble for Se ria l Cont rol Word

D7 (MSB)

D6

D5

D4

D3

D2

D1

D0 (LSB)

Attenuation (dB)

X

0

0

0

0

0

0

0

0

X

0

0

0

0

0

0

1

0.25

X

0

0

0

0

0

1

0

0.5

X

0

0

0

0

1

0

0

1

X

0

0

0

1

0

0

0

2

X

0

0

1

0

0

0

0

4

X

0

1

0

0

0

0

0

8

X

1

0

0

0

0

0

0

16

X

1

1

1

1

1

1

1

31.75

In the Serial Mode, the F1958 is programmed via the serial port on the rising edge of Latch Enable (LE). It is required that LE be kept logic

LOW until all data bits are clocked into the shift register. The F1958 will change attenuation state after the data word is latched into the active

register. Refer to Figure 33.