c8051t623-g Silicon Laboratories, c8051t623-g Datasheet - Page 245

• Manufacturer Part Number: c8051t623-g
• Description: Full Speed Usb Eprom Mcu Family
• Manufacturer: Silicon Laboratories

C8051T622/3 and C8051T326/7
25.2. C2 Pin Sharing
The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging and
EPROM programming functions may be performed. This is possible because C2 communication is typi-
cally 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 (normally RST) and C2D pins. In
most applications, external resistors are required to isolate C2 interface traffic from the user application
when performing debug functions. These external resistors are not necessary for production boards. A typ-
ical isolation configuration is shown in Figure 25.1.
The configuration in Figure 25.1 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.
252
Output (c)
RST (a)
Input (b)
Figure 25.1. Typical C2 Pin Sharing
C2 Interface Master
Rev. 1.1
C2CK
C2D