F1912 Datasheet

R35DS0055EU0100 Rev.1.00

Nov 10, 2022

Page 9

3.

Functional Description

3.1

Programming Options

F1912 can be programmed using either the parallel or serial interface, which is selectable via VMODE (pin 13).

Serial mode is selected by floating VMODE or pulling it to a voltage logic high (greater than VIH) and parallel mode

is selected by setting VMODE to logic low (less than VIL).

3.2

Serial Control Mode

F1912 Serial mode is selected by floating VMODE (pin 13) or pulling it to a voltage > VIH. The serial interface is a 6

bit shift register to shift in the data MSB (D5) first. When serial programming is used, all the parallel control input

pins (1, 15, 16, 17, 19, 20) must be grounded.

Table 1. 6 Bit SPI Word Sequence

D5

Attenuation 16 dB Control Bit

D4

Attenuator 8 dB Control Bit

D3

Attenuator 4 dB Control Bit

D2

Attenuator 2 dB Control Bit

D1

Attenuator 1 dB Control Bit

D0

Attenuator 0.5 dB Control Bit

Table 2. Truth Table for Serial Control Word

D5 (MSB)

D4

D3

D2

D1

D0 (LSB)

Attenuation (dB)

0

0

0

0

0

0

0

0

0

0

0

0

1

0.5

0

0

0

0

1

0

1

0

0

0

1

0

0

2

0

0

1

0

0

0

4

0

1

0

0

0

0

8

1

0

0

0

0

0

16

1

1

1

1

1

1

31.5

3.2.1.

Serial Mode Register Timing Diagram

With serial control, the F1912 can be programmed via the serial port on the rising edge of Latch Enable (LE),

which loads the last 6 DATA line bits [formatted MSB (D5) first] resident in the SHIFT register followed by the

next 5 bits.

Note The Timing Spec Intervals In Blue.