Datasheet

PIC16C745/765
DS41124D-page 112 Preliminary  1999-2013 Microchip Technology Inc.
FIGURE 13-8: WAKE-UP FROM SLEEP THROUGH INTERRUPT
13.10 Program Verification/Code Protection
If the code protection bit(s) have not been pro-
grammed, the on-chip program memory can be read
out for verification purposes.
13.11 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 read-
able and writable during program/verify. It is recom-
mended that only the four least significant bits of the ID
location are used.
13.12 In-Circuit Serial Programming
PIC16CXX microcontrollers can be serially pro-
grammed 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 firm-
ware to be programmed.
The device is placed into a program/verify mode by
holding the RB6 and RB7 pins low, while raising the
MCLR
(VPP) pin from VIL to VIHH (see programming
specification). RB6 becomes the programming clock
and RB7 becomes the programming data. Both RB6
and RB7 are Schmitt Trigger inputs in this mode.
After RESET, to place the device into programming/
verify mode, the program counter (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 if
the command was a load or a read. For complete
details of serial programming, please refer to the
PIC16C6X/7X Programming Specifications (Literature
#DS30228).
FIGURE 13-9: TYPICAL IN-CIRCUIT SERIAL
PROGRAMMING
CONNECTION
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
CLKOUT
(4)
INT pin
INTF flag
(INTCON<1>)
GIE bit
(INTCON<7>)
INSTRUCTION FLOW
PC
Instruction
fetched
Instruction
executed
PC PC+1 PC+2
Inst(PC) = SLEEP
Inst(PC - 1)
Inst(PC + 1)
SLEEP
Processor in
SLEEP
Interrupt Latency
(2)
Inst(PC + 2)
Inst(PC + 1)
Inst(0004h)
Inst(0005h)
Inst(0004h)
Dummy cycle
PC + 2 0004h 0005h
Dummy cycle
T
OST
(2)
PC+2
Note 1: HS oscillator mode assumed.
2: T
OST = 1024TOSC (drawing not to scale). This delay is not present in EC osc mode.
3: GIE = '1' assumed. After wake-up, the processor jumps to the interrupt routine. If GIE = '0', execution will continue in-line.
4: CLKOUT is not available in these osc modes, but shown here for timing reference.
Note: Microchip does not recommend code pro-
tecting windowed devices. Devices that are
code protected may be erased, but not pro-
grammed again.
External
Connector
Signals
To N o r m a l
Connections
To N o r m a l
Connections
PIC16CXX
V
DD
VSS
MCLR/VPP
RB6
RB7
+5V
0V
V
PP
CLK
Data I/O
VDD