C8051F989-GUR Silicon Labs, C8051F989-GUR Datasheet - Page 101

• Manufacturer Part Number: C8051F989-GUR
• Description: 8-bit Microcontrollers - MCU 4kB 512B RAM
• Manufacturer: Silicon Labs

Specifications of C8051F989-GUR

• Rohs: yes
• Core: 8051
• Data Bus Width: 8 bit
• Processor Series: C8051

8.8.
CS0 can be configured to automatically scan a sequence of contiguous CS0 input channels by configuring
and enabling auto-scan. Using auto-scan with the CS0 comparator interrupt enabled allows a system to
detect a change in measured capacitance without requiring any additional dedicated MCU resources.
Auto-scan is enabled by setting the CS0 start-of-conversion bits (CS0CF6:4) to 111b. After enabling auto-
scan, the starting and ending channels should be set to appropriate values in CS0SS and CS0SE,
respectively. Writing to CS0SS when auto-scan is enabled will cause the value written to CS0SS to be
copied into CS0MX. After being enabled, writing a 1 to CS0BUSY will start auto-scan conversions. When
auto-scan completes the number of conversions defined in the CS0 accumulator bits (CS0CF1:0), auto-
scan configures CS0MX to the next sequential port pin configured as an analog input and begins a
conversion on that channel. All other pins between CS0SS and CS0SE which are set as analog inputs are
grounded during the conversion. This scan sequence continues until CS0MX reaches the ending input
channel value defined in CS0SE. After one or more conversions have been taken at this channel, auto-
scan configures CS0MX back to the starting input channel. For an example system configured to use auto-
scan, please see Figure “8.2 Auto-Scan Example” on page 101.
Note: Auto-scan attempts one conversion on a CS0MX channel regardless of whether that channel’s port pin has
If auto-scan is enabled when the device enters suspend mode, auto-scan will remain enabled and running.
This feature allows the device to wake from suspend through CS0 greater-than comparator event on any
configured capacitive sense input included in the auto-scan sequence of inputs.
P2MDIN = 0xF2
P3MDIN = 0x04
CS0CN = 0x80
CS0SE = 0x0D
CS0CF = 0x70
CS0SS = 0x02
been configured as an analog input. Auto-scan will also complete the current rotation when the device is halted
for debugging.
Automatic Scanning (Method 1—CS0SMEN = 0)
SFR Configuration:
Configures P3.0-P3.1
and P3.3-P3.7 as
analog inputs
Enables CS0
Enables Auto-scan
as start-of-
conversion source
Sets P2.2 as Auto-
scan starting channel
Sets P3.5 as Auto-
scan ending channel
Configures P2.3,
P2.2, P2.0 as analog
inputs
Figure 8.2. Auto-Scan Example
Rev. 1.1
C8051F99x-C8051F98x
A
D
A
A
D
D
D
D
A
A
D
A
A
A
A
A
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
P3.0
P3.1
P3.2
P3.3
P3.4
P3.5
P3.6
P3.7
. . .
10
11
12
13
14
15
0
1
2
3
4
5
6
7
8
9
analog inputs result
Scans on channels
values that cannot
not configured as
in indeterminate
Interrupt event
Greater Than
trigger a CS0
101