C8051F352 Datasheet, PDF (68/234 Pages) Silicon Laboratories – 8 k ISP Flash MCU Family

C8051F350/1/2/3
6.1. IDAC Output Scheduling
A flexible output update mechanism allows for seamless full-scale changes and supports jitter-free
updates for waveform generation. Three update modes are provided, allowing IDAC output updates on a
write to the IDAC’s data register, on a Timer overflow, or on an external pin edge.
6.1.1. Update Output On-Demand
In its default mode (IDAnCN.[6:4] = ‘111’) the IDAC output is updated “on-demand” with a write to the data
register (IDAn). In this mode, data is immediately latched into the IDAC after a write to its data register.
6.1.2. Update Output Based on Timer Overflow
The IDAC output update can be scheduled on a Timer overflow. This feature is useful in systems where the
IDAC is used to generate a waveform of a defined sampling rate, by eliminating the effects of variable
interrupt latency and instruction execution on the timing of the IDAC output. When the IDAnCM bits
(IDAnCN.[6:4]) are set to ‘000’, ‘001’, ‘010’ or ‘011’, writes to the IDAC data register (IDAn) are held until an
associated Timer overflow event (Timer 0, Timer 1, Timer 2 or Timer 3, respectively) occurs, at which time
the data register contents are copied to the IDAC input latch, allowing the IDAC output to change to the
new value.
6.1.3. Update Output Based on CNVSTR Edge
The IDAC output can also be configured to update on a rising edge, falling edge, or both edges of the
external CNVSTR signal. When the IDAnCM bits (IDAnCN.[6:4]) are set to ‘100’, ‘101’, or ‘110’, writes to
the IDAC data register (IDAn) are held until an edge occurs on the CNVSTR input pin. The particular set-
ting of the IDAnCM bits determines whether the IDAC output is updated on rising, falling, or both edges of
CNVSTR. When a corresponding edge occurs, the data register contents are copied to the IDAC input
latch, allowing the IDAC output to change to the new value.
6.2. IDAC Output Mapping
The data word mapping for the IDAC is shown in Figure 6.2. The full-scale output current of the IDAC is
selected using the IDAnOMD bits (IDAnCN[1:0]). By default, the IDAC is set to a full-scale output current of
0.25 mA. The IDAnOMD bits can also be configured to provide full-scale output currents of 0.5 mA, 1 mA,
or 2 mA.
IDAn Data Word
(D7 – D0)
0x00
0x01
0x80
0xFF
Output Current vs IDAnOMD bit setting
‘11’ (2 mA)
‘10’ (1 mA)
‘01’ (0.5 mA)
‘00’ (0.25 mA)
0 mA
0 mA
0 mA
0 mA
1/256 x 2 mA
1/256 x 1 mA
1/256 x 0.5 mA 1/256 x 0.25 mA
128/256 x 2 mA 128/256 x 1 mA 128/256 x 0.5 mA 128/256 x 0.25 mA
255/256 x 2 mA 255/256 x 1 mA 255/256 x 0.5 mA 255/256 x 0.25 mA
Figure 6.2. IDAC Data Word Mapping
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