Texas Instruments MSP50C614 manual Overflow bits Least-significant data value Ignored bits

Models: MSP50C614

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Digital-to-Analog Converter (DAC)

DAC Control register

 

 

 

 

 

 

Address 0x34

 

 

(4-bit wide location)

 

 

 

03

02

01

00

 

 

 

 

 

 

 

Set DAC resolution to

8 bits:

 

DM

E

0

0

Set DAC resolution to

9 bits:

 

DM

E

0

1

Set DAC resolution to 10 bits:

 

DM

E

1

0

 

 

 

 

DM : Drive Mode selection

(0 = C3x style

: 1 = C5x style)

E : pulse-density-modulation Enable (overall DAC enable) 0x0 : default state of register after RESET low

Bit 2 in the DAC control register is used to enable/disable the pulse-density modulation. This bit must be set in order to enable the overall functionality of the DAC. After RESET is held low, the default state of bit 2 is clear. In this state, the output at the DAC pins is guaranteed to be zero (no PDM pulsing). During DAC activity, the PDM enable bit may also be toggled at any time to achieve the zero state. In other words, toggling the PDM enable bit from high-to-low-to- high brings the DAC output to the known state of zero.

Note: PDM Enable Bit

By default, the PDM enable bit is cleared: DAC function is off.

Data values are output to the DAC by writing to the DAC data register, address 0x30. The highest-priority interrupt, INT0, is generated at the sampling rate governed by the ClkSpdCtrl and the DAC control register. The program in software is responsible for writing a correctly-scaled DAC value to the DAC data register, in response to each INT0 interrupt. The register at 0x30 is 16-bits wide. The data is written in sign-magnitude format. Bit 15 of the register is the sign bit. Bits 14 and 13 are the overflow bits. Bits 12 through 3 are the data-value bits: The MSB is bit 12, and the LSB is bit 5, 4, or 3, depending on the resolution.

DAC Data register

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Address 0x30

(16-bit wide location)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Write Only

15

14

13

12

11

10

09

08

07

06

05

04

03

02

01

00

10 bit DAC resolution:

S

O

O

 

M

D

D

D

D

D

D

D

 

D

 

L

 

X

X

X

9 bit DAC resolution:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

S

O

O

 

M

D

D

D

D

D

D

D

 

L

 

 

X

X

X

X

 

8 bit DAC resolution:

S

O

O

 

M

D

D

D

D

D

D

L

 

 

X

 

X

X

X

X

 

S : Sign bit

M : Most-significant data value

 

D ; Data (magnitude)

 

 

 

 

 

 

 

 

 

 

 

O : Overflow bits

L : Least-significant data value

 

X : ignored bits

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The overflow bits function in different ways, depending on the drive mode selected. The two DAC drive modes are informally named C3x style and C5x

Peripheral Functions

3-9

Page 79
Image 79
Texas Instruments MSP50C614 manual Overflow bits Least-significant data value Ignored bits