C8051F360 datasheet(185/288 Pages) SILABS

185 / 288 page

Rev. 1.0

185

C8051F360/1/2/3/4/5/6/7/8/9

17.1. Priority Crossbar Decoder

The Priority Crossbar Decoder (Figure 17.3) assigns a priority to each I/O function, starting at the top with

UART0. When a digital resource is selected, the least-significant unassigned Port pin is assigned to that

resource (excluding UART0, which will be assigned to specific port pins (P0.1 and P0.2 in the

C8051F360/3 devices, P0.4 and P0.5 in the C8051F361/2/4/5/6/7/8/9 devices). If a Port pin is assigned,

the Crossbar skips that pin when assigning the next selected resource. Additionally, the Crossbar will skip

Port pins whose associated bits in the PnSKIP registers are set. The PnSKIP registers allow software to

skip Port pins that are to be used for analog input, dedicated functions, or GPIO.

Important Note on Crossbar Configuration: If a Port pin is claimed by a peripheral without use of the

Crossbar, its corresponding PnSKIP bit should be set. This applies to the port pins associated with the

external oscillator, VREF, external CNVSTR signal, IDA0, and any selected ADC or comparator inputs. The

Crossbar skips selected pins as if they were already assigned, and moves to the next unassigned pin.

Figure 17.3 shows the Crossbar Decoder priority with no Port pins skipped (P0SKIP, P1SKIP, P2SKIP,

P3SKIP = 0x00); Figure 17.4 shows the Crossbar Decoder priority with the P1.0 and P1.1 pins skipped

(P1SKIP = 0x03).

01234567012345670123456701234

567

(*4-Wire SPI Only)

CP0

CP0A

CP1

CP1A

/SYSCLK

CEX0

CEX1

CEX2

CEX3

CEX4

CEX5

ECI

00000000000000000000000000000

000

P3SKIP[0:7]

P3.1-P3.4

available on

32/48-pin only

P3.5-P3.7

available

on 48-pin

only

P2SKIP[0:7]

(48-pin package)

(32-pin and 28-pin packages)

P1SKIP[0:7]

NSS*

SCK

MISO

MOSI

RX0

SF Signals

(32- and 28-

pin)

PIN I/O

TX0

SF Signals

(48-pin)

TX0

RX0

SDA

P0SKIP[0:7]

SCL

Figure 17.3. Crossbar Priority Decoder with No Pins Skipped

C8051F360 Datasheet(PDF) 185 Page - Silicon Laboratories

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