P12C508 Microchip Technology, P12C508 Datasheet - Page 36

• Manufacturer Part Number: P12C508
• Description: 8-Pin / 8-Bit CMOS Microcontroller
• Manufacturer: Microchip Technology

PIC12C5XX
7.12
The PIC12C5XX microcontrollers 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 customers 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 programmed.
The device is placed into a program/verify mode by
holding the GP1 and GP0 pins low while raising the
MCLR (V
specification). GP1 becomes the programming clock
and GP0 becomes the programming data. Both GP1
and GP0 are Schmitt Trigger inputs in this mode.
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.
A typical in-circuit serial programming connection is
shown in Figure 7-15.
DS40139A-page 36
In-Circuit Serial Programming
PP
) pin from V
IL
to V
IHH
(see programming
Advanced Information
FIGURE 7-15: TYPICAL IN-CIRCUIT SERIAL
External
Connector
Signals
Data I/O
CLK
+5V
V
0V
PP
PROGRAMMING
CONNECTION
To Normal
Connections
To Normal
Connections
1996 Microchip Technology Inc.
V
V
MCLR/V
GP1
GP0
V
DD
SS
DD
PIC12C5XX
PP