C8051F045 View Datasheet(PDF) - Silicon Laboratories
Part Name
Description
Manufacturer
C8051F045 Datasheet PDF : 328 Pages
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C8051F040/1/2/3/4/5/6/7
1.4. Programmable Digital I/O and Crossbar
The standard 8051 Ports (0, 1, 2, and 3) are available on the MCUs. The C8051F040/2/4/6 have 4 addi-
tional 8-bit ports (4, 5, 6, and 7) for a total of 64 general-purpose I/O Ports. The Ports behave like the stan-
dard 8051 with a few enhancements.
Each port pin can be configured as either a push-pull or open-drain output. Also, the "weak pullups" which
are normally fixed on an 8051 can be globally disabled, providing additional power saving capabilities for
low-power applications.
Perhaps the most unique enhancement is the Digital Crossbar. This is essentially a large digital switching
network that allows mapping of internal digital system resources to Port I/O pins on P0, P1, P2, and P3
(See Figure 1.9). Unlike microcontrollers with standard multiplexed digital I/O ports, all combinations of
functions are supported with all package options offered.
The on-chip counter/timers, serial buses, HW interrupts, ADC Start of Conversion input, comparator out-
puts, and other digital signals in the controller can be configured to appear on the Port I/O pins specified in
the Crossbar Control registers. This allows the user to select the exact mix of general purpose Port I/O and
digital resources needed for the particular application.
Highest
Priority
Lowest
Priority
Port
Latches
UART0
2
4
SPI
2
SMBus
2
UART1
6
PCA
XBR0, XBR1, XBR2,
XBR3 P1MDIN,
P2MDIN, P3MDIN
Registers
P0MDOUT, P1MDOUT,
P2MDOUT, P3MDOUT
Registers
Priority
Decoder
8
P0
I/O
Cells
Comptr.
2
Outputs
T0, T1,
T2, T2EX,
T3, T3EX,
8
T4,T4EX,
/INT0,
/INT1
/SYSCLK
CNVSTR0
CNVSTR2
8
P0 (P0.0-P0.7)
8
P1 (P1.0-P1.7)
8
P2 (P2.0-P2.7)
8
P3 (P3.0-P3.7)
Digital
Crossbar
8
P1
I/O
Cells
8
P2
I/O
Cells
8
P3
I/O
Cells
To External
Memory
Interface
(EMIF)
To
ADC2
Input
To
Comparators
To
ADC0
Input
Figure 1.9. Digital Crossbar Diagram
External
Pins
P0.0
P0.7
Highest
Priority
P1.0
P1.7
P2.0
P2.7
P3.0
P3.7
Lowest
Priority
Rev. 1.5
29
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