C8051F521A-IM View Datasheet(PDF) - Silicon Laboratories

Part Name

Description

Manufacturer

C8051F521A-IM

8/4/2 kB ISP Flash MCU Family

Silicon Laboratories 

C8051F52x/F53x

21.2. C2 Pin Sharing

The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging and

Flash programming functions may be performed. This is possible because C2 communication is typically

performed when the device is in the halt state, where all on-chip peripherals and user software are stalled.

In this halted state, the C2 interface can safely ‘borrow’ the C2CK (/RST) and C2D (P0.1 or P0.6) pins. In

most applications, external resistors are required to isolate C2 interface traffic from the user application. A

typical isolation configuration is shown in Figure 21.1.

C8051Fxxx

/Reset (a)

Input (b)

Output (c)

C2CK

C2D

C2 Interface Master

Figure 21.1. Typical C2 Pin Sharing

The configuration in Figure 21.1 assumes the following:

1. The user input (b) cannot change state while the target device is halted.

2. The /RST pin on the target device is used as an input only.

Additional resistors may be necessary depending on the specific application.

216

Rev. 1.4

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