PIC12C5XX
8.12
In-Circuit Serial Programming
FIGURE 8-16: TYPICAL IN-CIRCUIT SERIAL
PROGRAMMING
The PIC12C5XX microcontrollers with EPROM pro-
gram memory can be serially programmed while in the
end application circuit. This is simply done with two
lines for clock and data, and three other lines for power,
ground, and the programming voltage. This allows cus-
tomers to manufacture boards with unprogrammed
devices, and then program the microcontroller just
before shipping the product. This also allows the most
recent firmware or a custom firmware to be pro-
grammed.
CONNECTION
To Normal
Connections
External
Connector
Signals
PIC12C5XX
+5V
0V
VDD
VSS
VPP
MCLR/VPP
The device is placed into a program/verify mode by
holding the GP1 and GP0 pins low while raising the
MCLR (VPP) pin from VIL to VIHH (see programming
specification). GP1 becomes the programming clock
and GP0 becomes the programming data. Both GP1
and GP0 are Schmitt Trigger inputs in this mode.
GP1
GP0
CLK
Data I/O
VDD
After reset, a 6-bit command is then supplied to the
device. Depending on the command, 14-bits of pro-
gram data are then supplied to or from the device,
depending if the command was a load or a read. For
complete details of serial programming, please refer to
the PIC12C5XX Programming Specifications.
To Normal
Connections
A typical in-circuit serial programming connection is
shown in Figure 8-16.
DS40139E-page 46
1999 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
