Pin-Sha�Ed - Holtek BS83B24C Manual

BS83B24C/BS83C40C
Touch Flash MCU
• SLEDC2 Register – BS83C40C
Bit 7
Name —
R/W —
POR —
Bit 7~6 Unimplemented, read as "0"
Bit 5~4 SLEDC25~SLEDC24: PF1~PF0 Source Current Selection
00: Source current=Level 0 (min.)
01: Source current=Level 1
10: Source current=Level 2
11: Source current=Level 3 (max.)
Bit 3~2 SLEDC23~SLEDC22: PE7~PE4 Source Current Selection
00: Source current=Level 0 (min.)
01: Source current=Level 1
10: Source current=Level 2
11: Source current=Level 3 (max.)
Bit 1~0 SLEDC21~SLEDC20: PE3~PE0 Source Current Selection
00: Source current=Level 0 (min.)
01: Source current=Level 1
10: Source current=Level 2
11: Source current=Level 3 (max.)
Pin-shared Functions
The flexibility of the microcontroller range is greatly enhanced by the use of pins that have more than
one function. Limited numbers of pins can force serious design constraints on designers but by supplying
pins with multi-functions, many of these difficulties can be overcome. For these pins, the desired function
of the multi-function I/O pins is selected by a series of registers via the application program control.
Pin-shared Function Selection Registers
The limited number of supplied pins in a package can impose restrictions on the amount of functions
a certain device can contain. However by allowing the same pins to share several different functions
and providing a means of function selection, a wide range of different functions can be incorporated
into even relatively small package sizes. The devices include Port "x" output function Selection
register "n", labeled as PxSn, and Input Function Selection register, labeled as IFS, which can select
the desired functions of the multi-function pin-shared pins.
When the pin-shared input function is selected to be used, the corresponding input and output
functions selection should be properly managed. For example, if the I
correnspinding pin-shared function should be configured as the SDA/SDI/RX function by configuring
the PASn register and the SDA signal input should be properly selected using the IFS register.
However, if the external interrupt function is selected to be used, the relevant output pin-shared
function should be selected as an I/O function and the interrupt input signal should be selected.
The most important point to note is to make sure that the desired pin-shared function is properly
selected and also deselected. For most pin-shared functions, to select the desired pin-shared function,
the pin-shared function should first be correctly selected using the corresponding pin-shared control
register. After that the corresponding peripheral functional setting should be configured and then
the peripheral function can be enabled. However, special point must be noted for some digital input
pins, such as INT, xTCK, etc, which share the same pin-shared control configuration with their
corresponding general purpose I/O functions when setting the relevant functions, in addition to the
necessary pin-shared control and peripheral functional setup aforementioned, they must also be
setup as input by setting the corresponding bit in the I/O port control register. To correctly deselect
the pin-shared function, the peripheral function should first be disabled and then the corresponding
pin-shared function control register can be modified to select other pin-shared functions.
Rev. 1.00
6 5 4
— SLEDC�5 SLEDC�4 SLEDC�3 SLEDC�� SLEDC�1 SLEDC�0
— R/W R/W
— 0 0
69
3 2 1
R/W R/W R/W
0 0 0
C SDA line is used, the
2
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0
R/W
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