Specifications

C8051F330/1
Rev. 1.1 203
20.2. C2 Pin Sharing
The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging, FLASH program-
ming, and boundary scan functions may be performed. This is possible because C2 communication is typically per-
formed 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 (P2.0) 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 20.6.
The configuration in Figure 20.6 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.
C2D
C2CK
/Reset (a)
Input (b)
Output (c)
C2 Interface Master
C8051Fxxx
Figure 20.6. Typical C2 Pin Sharing