C8051F120/1/2/3/4/5/6/7
Rev. 1.2
217
19.1. Ports 0 through 3 and the Priority Crossbar Decoder
The Priority Crossbar Decoder, or “Crossbar”, allocates and assigns Port pins on Port 0 through Port 3 to the digital
peripherals (UARTs, SMBus, PCA, Timers, etc.) on the device using a priority order. The Port pins are allocated in
order starting with P0.0 and continue through P3.7 if necessary. The digital peripherals are assigned Port pins in a pri-
ority order which is listed in Figure 19.3, with UART0 having the highest priority and CNVSTR2 having the lowest
priority.
19.1.1. Crossbar Pin Assignment and Allocation
The Crossbar assigns Port pins to a peripheral if the corresponding enable bits of the peripheral are set to a logic 1 in
the Crossbar configuration registers XBR0, XBR1, and XBR2, shown in Figure 19.7, Figure 19.8, and Figure 19.9.
For example, if the UART0EN bit (XBR0.2) is set to a logic 1, the TX0 and RX0 pins will be mapped to P0.0 and
P0.1 respectively. Because UART0 has the highest priority, its pins will always be mapped to P0.0 and P0.1 when
UART0EN is set to a logic 1. If a digital peripheral’s enable bits are not set to a logic 1, then its ports are not accessi-
Figure 19.3. Priority Crossbar Decode Table
PIN I/O 0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
TX0
●
RX0
●
SCK
●
●
MISO
●
●
MOSI
●
●
NSS
●
●
NSS is not assigned to a port pin when the SPI is placed in 3-wire mode
SDA
●
● ● ● ● ●
SCL
●
● ● ● ● ●
TX1
●
● ● ● ● ● ● ●
RX1
●
● ● ● ● ● ● ●
CEX0
●
● ● ● ● ● ● ● ● ●
CEX1
●
● ● ● ● ● ● ● ● ●
CEX2
●
● ● ● ● ● ● ● ● ●
CEX3
●
● ● ● ● ● ● ● ● ●
CEX4
●
● ● ● ● ● ● ● ● ●
CEX5
●
● ● ● ● ● ● ● ● ●
ECI
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
ECI0E: XBR0.6
CP0
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
CP0E: XBR0.7
CP1
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
CP1E: XBR1.0
T0
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
T0E: XBR1.1
/INT0
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
INT0E: XBR1.2
T1
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
T1E: XBR1.3
/INT1
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
INT1E: XBR1.4
T2
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
T2E: XBR1.5
T2EX
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
T2EXE: XBR1.6
T4
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
T4E: XBR2.3
T4EX
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
T4EXE: XBR2.4
/SYSCLK
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
SYSCKE: XBR1.7
CNVSTR0
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
CNVSTE0: XBR2.0
CNVSTR2
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
CNVSTE2: XBR2.5
ALE
/RD
/W
R
A
IN1
.0
/A
8
A
IN1
.1
/A
9
A
IN1
.2
/A
1
0
A
IN1
.3
/A
1
1
A
IN1
.4
/A
1
2
A
IN1
.5
/A
1
3
A
IN1
.6
/A
1
4
A
IN1
.7
/A
1
5
A8m/
A0
A9m/
A1
A10m/
A
2
A11m/
A
3
A12m/
A
4
A13m/
A
5
A14m/
A
6
A15m/
A
7
AD0/
D0
AD1/
D1
AD2/
D2
AD3/
D3
AD4/
D4
AD5/
D5
AD6/
D6
AD7/
D7
XBR2.2
XBR0.[5:3]
UART0EN:
SPI0EN:
Crossbar Register Bits
XBR0.2
XBR0.1
XBR0.0
SMB0EN:
AIN1 Inputs/Non-muxed Addr H Muxed Addr H/Non-muxed Addr L
Muxed Data/Non-muxed Data
UART1EN:
PCA0ME:
P0
P1
P2
P3
Summary of Contents for C8051F120
Page 2: ...C8051F120 1 2 3 4 5 6 7 2 Rev 1 2 Notes ...
Page 8: ...C8051F120 1 2 3 4 5 6 7 8 Rev 1 2 26 2 Flash Programming Commands 318 26 3 Debug Support 321 ...
Page 16: ...C8051F120 1 2 3 4 5 6 7 16 Rev 1 2 Notes ...
Page 48: ...C8051F120 1 2 3 4 5 6 7 48 Rev 1 2 ...
Page 98: ...C8051F120 1 2 3 4 5 6 7 98 Rev 1 2 ...
Page 106: ...C8051F120 1 2 3 4 5 6 7 106 Rev 1 2 Notes ...
Page 183: ...C8051F120 1 2 3 4 5 6 7 Rev 1 2 183 Notes ...
Page 184: ...C8051F120 1 2 3 4 5 6 7 184 Rev 1 2 ...
Page 214: ...C8051F120 1 2 3 4 5 6 7 214 Rev 1 2 Notes ...