Datasheet

 2010 Microchip Technology Inc. DS41190G-page 69
PIC12F629/675
9.8 Code Protection
If the code protection bit(s) have not been
programmed, the on-chip program memory can be
read out for verification purposes.
9.9 ID Locations
Four memory locations (2000h-2003h) are designated
as ID locations where the user can store checksum or
other code identification numbers. These locations are
not accessible during normal execution but are
readable and writable during Program/Verify. Only the
Least Significant 7 bits of the ID locations are used.
9.10 In-Circuit Serial Programming
The PIC12F629/675 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
• 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 GP0 and GP1 pins low, while raising the
MCLR
(VPP) pin from VIL to VIHH (see Programming
Specification). GP0 becomes the programming data
and GP1 becomes the programming clock. Both GP0
and GP1 are Schmitt Trigger inputs in this mode.
After Reset, to place the device into Programming/
Verify mode, the PC is at location 00h. A 6-bit
command is then supplied to the device. Depending on
the command, 14-bits of program data are then
supplied to or from the device, depending on whether
the command was a load or a read. For complete
details of serial programming, please refer to the
Programming Specifications.
A typical In-Circuit Serial Programming connection is
shown in Figure 9-14.
FIGURE 9-14: TYPICAL IN-CIRCUIT
SERIAL PROGRAMMING
CONNECTION
9.11 In-Circuit Debugger
Since in-circuit debugging requires the loss of clock,
data and MCLR
pins, MPLAB
®
ICD 2 development with
an 8-pin device is not practical. A special 14-pin
PIC12F675-ICD device is used with MPLAB ICD 2 to
provide separate clock, data and MCLR
pins and frees
all normally available pins to the user.
This special ICD device is mounted on the top of the
header and its signals are routed to the MPLAB ICD 2
connector. On the bottom of the header is an 8-pin
socket that plugs into the user’s target via the 8-pin
stand-off connector.
When the ICD
pin on the PIC12F675-ICD device is
held low, the In-Circuit Debugger functionality is
enabled. This function allows simple debugging
functions when used with MPLAB ICD 2. When the
microcontroller has this feature enabled, some of the
resources are not available for general use. Table 9-10
shows which features are consumed by the
background debugger:
TABLE 9-10: DEBUGGER RESOURCES
For more information, see 8-Pin MPLAB ICD 2 Header
Information Sheet (DS51292) available on Microchip’s
web site (www.microchip.com).
Note: The entire data EEPROM and Flash
program memory will be erased when the
code protection is turned off. The INTOSC
calibration data is also erased. See
PIC12F629/675 Programming Specifica-
tion for more information.
I/O pins ICDCLK, ICDDATA
Stack 1 level
Program Memory Address 0h must be NOP
300h-3FEh
External
Connector
Signals
To N or ma l
Connections
To N or ma l
Connections
PIC12F629/675
V
DD
VSS
GP3/MCLR/VPP
GP1
GP0
+5V
0V
V
PP
CLK
Data I/O
V
DD