C8051F581-IMR Silicon Labs, C8051F581-IMR Datasheet - Page 353

• Manufacturer Part Number: C8051F581-IMR
• Description: 8-bit Microcontrollers - MCU 50MIPS 128kB 8kB SPI
• Manufacturer: Silicon Labs

Specifications of C8051F581-IMR

• Rohs: yes
• Core: 8051
• Processor Series: C8051
• Data Bus Width: 8 bit

30.2. C2 Pin Sharing
The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging and
Flash programming 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 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 30.1.
The configuration in Figure 30.1 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.
Output (c)
RST (a)
Input (b)
Figure 30.1. Typical C2 Pin Sharing
C2 Interface Master
Rev. 1.2
C2CK
C2D
C8051Fxxx
C8051F58x/F59x
353