MC9S12E128CFUE Datasheet, PDF (243/606 Pages) Freescale Semiconductor, Inc – MC9S12E128 Data Sheet

Chapter 7 Digital-to-Analog Converter (DAC8B1CV1)
7.4 Functional Description
The DAC8B1C module consists of analog and digital sub-blocks.
7.4.1 Functional Description
Data to be converted is written to DACD register. The data can be mapped either to left end or right end of
DACD register by clearing or setting DJM bit of DACC0 register. Also, the data written to DACD can be
a signed or unsigned data depending on DSGN bit of DACC0 register. See Table 7-3 below for data
formats. The maximum unsigned data that can be written to DACD register is $FF while the minimum
value is $00. If the data is signed, the maximum value that can be written to DACD is $7F while the
minimum value is $80, where $7F (signed) corresponds to $FF (unsigned) and $80 (signed) corresponds
to $00 (unsigned). Table 7-4 shows this characteristic between signed, unsigned data values and their
corresponding voltage output. See Table 7-4 for DAC signed and un-signed data and DAC output codes.
Table 7-3. Data Formats
DJM
0
0
1
1
DSGN
0
1
0
1
Description and Bus Bit Mapping
8 bit/left justified/unsigned — bits 15–8
8 bit/left justified/signed — bits 15–8
8 bit/right justified/unsigned — bits 7–0
8 bit/right justified/signed bits — 7–0
Table 7-4. Signed and Unsigned Data
and DAC Output Codes
Input signal
V_RL = 0
V_REF/V_RH = 5.12volts
5.12
5.08
5.07
Signed
8-Bit
Codes
7F
7E
7D
Unsigned
8-Bit
Codes
FF
FE
FD
2.580
2.56
2.54
2.52
01
81
00
80
FF
7F
FE
7E
0.020
0.000
81
01
80
00
MC9S12E128 Data Sheet, Rev. 1.07
Freescale Semiconductor
243