MICROCHIP PIC16C9XX Technical data
PIC16C9XX
8-Bit CMOS Microcontroller with LCD Driver
Devices included in this data sheet:
• PIC16C923
• PIC16C924
Microcontroller Core Features:
• High performance RISC CPU
• Only 35 single word instructions to learn
• 4K x 14 on-chip EPROM program memory
• 176 x 8 general purpose registers (SRAM)
• All single cycle instructions (500 ns) except for
program branches which are two-cycle
• Operating speed: DC - 8 MHz clock input
DC - 500 ns instruction cycle
• Interrupt capability
• Eight level deep hardware stack
• Direct, indirect and relative addressing modes
Peripheral Features:
• 25 I/O pins with individual direction control
• 25-27 input only pins
• Timer0: 8-bit timer/counter with 8-bit prescaler
• Timer1: 16-bit timer/counter, can be incremented
during sleep via external crystal/clock
• Timer2: 8-bit timer/counter with 8-bit period register, prescaler and postscaler
• One pin that can be configured a capture input,
PWM output, or compare output
- Capture is 16-bit, max. resolution 31.25 ns
- Compare is 16-bit, max. resolution 500 ns
- PWM max resolution is 10-bits.
Maximum PWM frequency @ 8-bit resolution
= 32 kHz, @ 10-bit resolution = 8 kHz
• Programmable LCD timing module
- Multiple LCD timing sources available
- Can drive LCD panel while in Sleep mode
- Static, 1/2, 1/3, 1/4 multiplex
- Static drive and 1/3 bias capability
- 16 bytes of dedicated LCD RAM
- Up to 32 segments, up to 4 commons
Common Segment Pixels
13232
23162
33090
4 29 116
Available in Die Form
• Synchronous Serial Port (SSP) with SPI
2
and I
• 8-bit multi-channel Analog to Digital converter
(PIC16C924 only)
C
Special Microcontroller Features:
• Power-on Reset (POR)
• Power-up Timer (PWRT) and Oscillator Start-up
Timer (OST)
• Watchdog Timer (WDT) with its own on-chip RC
oscillator for reliable operation
• Programmable code-protection
• Power saving SLEEP mode
• Selectable oscillator options
• In-Circuit Serial Programming™ (via two pins)
CMOS Tec hnology
• Low-power, high-speed CMOS EPROM
technology
• Fully static design
• Wide operating voltage range: 2.5V to 6.0V
• Commercial and Industrial temperature ranges
• Low-power consumption:
- < 2 mA @ 5.5V, 4 MHz
- 22.5 µ A typical @ 4V, 32 kHz
- < 1 µ A typical standby current @ 3.0V
ICSP is a trademark of Microchip Technology Inc. I
1997 Microchip Technology Inc. DS30444E - page 1
2
C is a trademark of Philips Corporation. SPI is a trademark of Motorola Corporation.
PIC16C9XX
Pin Diagrams
Shrink PDIP (750 mil)
MCLR/VPP
RB3
RB2
RA0
RA1
V
RA2
RA3
RA4/T0CKI
RA5/SS
RB1
RB0/INT
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
V
LCD2
V
LCD3
V
VSS
OSC1/CLKIN
OSC2/CLKOUT
RC0/T1OSO/T1CKI
RC1/T1OSI
RC2/CCP1
VLCD1
VLCDADJ
RD0/SEG00
RD1/SEG01
RD2/SEG02
RD3/SEG03
SS
C1
C2
DD
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
64
63
62
61
60
59
58
57
56
55
54
PIC16C923
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
RC0/T1OSO/T1CKI
RB4
RB5
RB7
RB6
DD
V
COM0
RD7/SEG31/COM1
RD6/SEG30/COM2
RD5/SEG29/COM3
RG6/SEG26
RG5/SEG25
RG4/SEG24
RG3/SEG23
RG2/SEG22
RG1/SEG21
RG0/SEG20
RF7/SEG19
RF6/SEG18
RF5/SEG17
RF4/SEG16
RF3/SEG15
RF2/SEG14
RF1/SEG13
RF0/SEG12
RE6/SEG11
RE5/SEG10
RE4/SEG09
RE3/SEG08
RE2/SEG07
RE1/SEG06
RE0/SEG05
RD4/SEG04
RA4/T0CKI
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
OSC1/CLKIN
OSC2/CLKOUT
RC0/T1OSO/T1CKI
PLCC
RA4/T0CKI
RA5/SS
RB0/INT
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
V
LCD2
V
LCD3
OSC1/CLKIN
OSC2/CLKOUT
RA5/SS
RB1
RB0/INT
C1
C2
V
LCD2
V
LCD3
VDD
VSS
RB1
V
VDD
VSS
/VPP
RA3
RA2
VSSRA1
RA0
RB2
RB3
MCLR
N/C
RB4
RB5
RB7
RB6
VDDCOM0
RD7/SEG31/COM1
RD6/SEG30/COM2
987654321
10
11
12
13
14
15
C1
C2
DD
16
17
PIC16C923
18
19
20
21
22
23
24
25
26
2728293031323334353637383940414243
LCD1
V
VLCDADJ
RC2/CCP1
RC1/T1OSI
RA3
RA2
VSSRA1
RA0
RB2
646362616059585756555453525150
1
2
3
4
5
6
7
8
PIC16C923
9
10
11
12
13
14
15
16
171819202122232425262728293031
RD0/SEG00
RD1/SEG01
RD2/SEG02
RD3/SEG03
MCLR/VPP
RB4
RB3
68676665646362
RE7/SEG27
RE0/SEG05
RE1/SEG06
RE2/SEG07
RD4/SEG04
VDDCOM0
RB5
RB7
RB6
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
RE3/SEG08
RE4/SEG09
RE6/SEG11
RE5/SEG10
RD7/SEG31/COM1
TQFP
RD6/SEG30/COM2
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
RD5/SEG29/COM3
RG6/SEG26
RG5/SEG25
RG4/SEG24
RG3/SEG23
RG2/SEG22
RG1/SEG21
RG0/SEG20
RG7/SEG28
RF7/SEG19
RF6/SEG18
RF5/SEG17
RF4/SEG16
RF3/SEG15
RF2/SEG14
RF1/SEG13
RF0/SEG12
RD5/SEG29/COM3
RG6/SEG26
RG5/SEG25
RG4/SEG24
RG3/SEG23
RG2/SEG22
RG1/SEG21
RG0/SEG20
RF7/SEG19
RF6/SEG18
RF5/SEG17
RF4/SEG16
RF3/SEG15
RF2/SEG14
RF1/SEG13
RF0/SEG12
LEGEND:
Input Pin
Output Pin
Input/Output Pin
Digital Input/LCD Output Pin
LCD Output Pin
DS30444E - page 2
LCD1
V
RC2/CCP1
RC1/T1OSI
VLCDADJ
RD0/SEG00
RD1/SEG01
RE0/SEG05
RD2/SEG02
RD3/SEG03
RD4/SEG04
RE1/SEG06
RE2/SEG07
RE3/SEG08
RE4/SEG09
RE6/SEG11
RE5/SEG10
1997 Microchip Technology Inc.
Pin Diagrams (Cont.’d)
PIC16C9XX
Shrink PDIP (750 mil)
MCLR/VPP
RB3
RB2
RA0/AN0
RA1/AN1
VSS
RA2/AN2
RA3/AN3/V
REF
RA4/T0CKI
RA5/AN4/SS
RB1
RB0/INT
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
V
LCD2
V
LCD3
V
VSS
OSC1/CLKIN
OSC2/CLKOUT
RC0/T1OSO/T1CKI
RC1/T1OSI
RC2/CCP1
LCD1
V
VLCDADJ
RD0/SEG00
RD1/SEG01
RD2/SEG02
RD3/SEG03
C1
C2
DD
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
64
63
62
61
60
59
58
57
56
55
54
PIC16C924
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
RC0/T1OSO/T1CKI
RB4
RB5
RB7
RB6
V
DD
COM0
RD7/SEG31/COM1
RD6/SEG30/COM2
RD5/SEG29/COM3
RG6/SEG26
RG5/SEG25
RG4/SEG24
RG3/SEG23
RG2/SEG22
RG1/SEG21
RG0/SEG20
RF7/SEG19
RF6/SEG18
RF5/SEG17
RF4/SEG16
RF3/SEG15
RF2/SEG14
RF1/SEG13
RF0/SEG12
RE6/SEG11
RE5/SEG10
RE4/SEG09
RE3/SEG08
RE2/SEG07
RE1/SEG06
RE0/SEG05
RD4/SEG04
RA4/T0CKI
RA5/AN4/SS
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
OSC1/CLKIN
OSC2/CLKOUT
RC0/T1OSO/T1CKI
PLCC
RA4/T0CKI
RA5/AN4/SS
RB0/INT
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
V
V
A
OSC1/CLKIN
OSC2/CLKOUT
TQFP
RB1
RB0/INT
C1
C2
V
LCD2
V
LCD3
VDD
VSS
RB1
LCD2
LCD3
VDD
VDD
VSS
/VPP
RA3/AN3/VREF
RA2/AN2
VSSRA1/AN1
RA0/AN0
RB2
RB3
MCLR
N/C
RB4
RB5
RB7
RB6
VDDCOM0
RD7/SEG31/COM1
RD6/SEG30/COM2
987654321
10
11
12
13
14
15
C1
C2
16
17
PIC16C924
18
19
20
21
22
23
24
25
26
2728293031323334353637383940414243
LCD1
V
VLCDADJ
RC2/CCP1
RC1/T1OSI
RA3/AN3/VREF
RA2/AN2
VSSRA1/AN1
RA0/AN0
RB2
646362616059585756555453525150
1
2
3
4
5
6
7
8
PIC16C924
9
10
11
12
13
14
15
16
171819202122232425262728293031
RD0/SEG00
RD1/SEG01
RD2/SEG02
RD3/SEG03
MCLR/VPP
RB4
RB3
68676665646362
RE7/SEG27
RE0/SEG05
RE1/SEG06
RE2/SEG07
RD4/SEG04
VDDCOM0
RB5
RB7
RB6
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
RE3/SEG08
RE4/SEG09
RE6/SEG11
RE5/SEG10
RD7/SEG31/COM1
RD6/SEG30/COM2
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
RD5/SEG29/COM3
RG6/SEG26
RG5/SEG25
RG4/SEG24
RG3/SEG23
RG2/SEG22
RG1/SEG21
RG0/SEG20
RG7/SEG28
RF7/SEG19
RF6/SEG18
RF5/SEG17
RF4/SEG16
RF3/SEG15
RF2/SEG14
RF1/SEG13
RF0/SEG12
RD5/SEG29/COM3
RG6/SEG26
RG5/SEG25
RG4/SEG24
RG3/SEG23
RG2/SEG22
RG1/SEG21
RG0/SEG20
RF7/SEG19
RF6/SEG18
RF5/SEG17
RF4/SEG16
RF3/SEG15
RF2/SEG14
RF1/SEG13
RF0/SEG12
LCD1
LEGEND:
Input Pin
Output Pin
Input/Output Pin
V
RC2/CCP1
RC1/T1OSI
VLCDADJ
RD0/SEG00
RD1/SEG01
RE0/SEG05
RD2/SEG02
RD3/SEG03
RD4/SEG04
RE1/SEG06
RE2/SEG07
RE3/SEG08
RE4/SEG09
RE6/SEG11
RE5/SEG10
Digital Input/LCD Output Pin
LCD Output Pin
1997 Microchip Technology Inc. DS30444E - page 3
PIC16C9XX
Table of Contents
1.0 General Description..................................................................................................................................................................... 5
2.0 PIC16C9XX Device Varieties...................................................................................................................................................... 7
3.0 Architectural Overview ................................................................................................................................................................ 9
4.0 Memory Organization................................................................................................................................................................ 17
5.0 Ports.......................................................................................................................................................................................... 31
6.0 Overview of Timer Modules....................................................................................................................................................... 43
7.0 Timer0 Module .......................................................................................................................................................................... 45
8.0 Timer1 Module .......................................................................................................................................................................... 51
9.0 Timer2 Module .......................................................................................................................................................................... 55
10.0 Capture/Compare/PWM (CCP) Module .................................................................................................................................... 57
11.0 Synchronous Serial Port (SSP) Module .................................................................................................................................... 63
12.0 Analog-to-Digital Converter (A/D) Module.................................................................................................................................79
13.0 LCD Module .............................................................................................................................................................................. 89
14.0 Special Features of the CPU...................................................................................................................................................103
15.0 Instruction Set Summary......................................................................................................................................................... 119
16.0 Development Support.............................................................................................................................................................. 137
17.0 Electrical Characteristics......................................................................................................................................................... 141
18.0 DC and AC Characteristics Graphs and Tables......................................................................................................................161
19.0 Packaging Information............................................................................................................................................................. 171
Appendix A: ................................................................................................................................................................................... 175
Appendix B: Compatibility ............................................................................................................................................................. 175
Appendix C: What’s New................................................................................................................................................................ 176
Appendix D: What’s Changed........................................................................................................................................................ 176
Index .................................................................................................................................................................................................. 177
List of Equations And Examples ........................................................................................................................................................ 181
List of Figures..................................................................................................................................................................................... 181
List of Tables...................................................................................................................................................................................... 182
Reader Response.............................................................................................................................................................................. 186
PIC16C9XX Product Identification System........................................................................................................................................ 187
To Our Valued Customers
We constantly strive to improve the quality of all our products and documentation. We have spent an exceptional
amount of time to ensure that these documents are correct. However, we realize that we may have missed a few
things. If you find any information that is missing or appears in error, please use the reader response form in the
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DS30444E - page 4
1997 Microchip Technology Inc.
PIC16C9XX
1.0 GENERAL DESCRIPTION
The PIC16C9XX is a family of
mance, CMOS, fully-static, 8-bit microcontrollers with
an integrated LCD Driver module, in the PIC16CXXX
mid-range family.
All PICmicro™ microcontrollers employ an advanced
RISC architecture. The PIC16CXXX microcontroller
family has enhanced core features, eight-level deep
stack, and multiple internal and external interrupt
sources. The separate instruction and data buses of the
Harvard architecture allow a 14-bit wide instruction
word with the separate 8-bit wide data. The two stage
instruction pipeline allows all instructions to execute in
a single cycle, except for program branches (which
require two cycles). A total of 35 instructions (reduced
instruction set) are available. Additionally, a large register set gives some of the architectural innov ations used
to achieve a very high performance.
PIC16CXXX microcontrollers typically achieve a 2:1
code compression and a 4:1 speed improvement over
other 8-bit microcontrollers in their class.
The PIC16C923 devices have 176 bytes of RAM and
25 I/O pins. In addition several peripheral features are
available including: three timer/counters, one Capture/Compare/PWM module, one serial port and one
LCD module. The Synchronous Serial P ort can be configured as either a 3-wire Serial Peripheral Interface
(SPI) or the two-wire Inter-Integrated Circuit (I
The LCD module features programmable multiplex
mode (static, 1/2, 1/3 and 1/4) and drive bias (static and
1/3). It is capable of driving up to 32 segments and up
to 4 commons. It can also drive the LCD panel while in
SLEEP mode.
The PIC16C924 devices have 176 bytes of RAM and
25 I/O pins. In addition several peripheral features are
available including: three timer/counters, one Capture/Compare/PWM module, one serial port and one
LCD module. The Synchronous Serial P ort can be configured as either a 3-wire Serial Peripheral Interface
(SPI) or the two-wire Inter-Integrated Circuit (I
The LCD module features programmable multiplex
mode (static, 1/2, 1/3 and 1/4) and drive bias (static and
1/3). It is capable of driving up to 32 segments and up
to 4 commons. It can also drive the LCD panel while in
SLEEP mode. The PIC16C924 also has an 5-channel
high-speed 8-bit A/D. The 8-bit resolution is ideally
suited for applications requiring low-cost analog interface, e.g. thermostat control, pressure sensing, and
meters.
The PIC16C9XX family has special features to reduce
external components, thus reducing cost, enhancing
system reliability and reducing power consumption.
There are four oscillator options, of which the single pin
RC oscillator provides a low-cost solution, the LP oscillator minimizes power consumption, XT is a standard
crystal, and the HS is for High Speed crystals. The
SLEEP (power-down) feature provides a power saving
low-cost, high-perfor-
2
C) bus.
2
C) bus.
mode. The user can wake up the chip from SLEEP
through several external and internal interrupts and
reset(s).
A highly reliable Watchdog Timer with its own on-chip
RC oscillator provides recovery in the event of a software lock-up.
A UV erasable CERQUAD (compatible with PLCC)
packaged version is ideal for code development while
the cost-effective One-Time-Programmable (OTP) version is suitable for production in any volume.
The PIC16C9XX family fits perfectly in applications
ranging from handheld meters, thermostats, to home
security products. The EPROM technology makes customization of application programs (LCD panels, calibration constants, sensor interfaces, etc.) extremely
fast and conv enient. The small f ootprint packages make
this microcontroller series perfect for all applications
with space limitations. Low cost, low pow er, high perf ormance, ease of use and I/O flexibility make the
PIC16C9XX very versatile even in areas where no
microcontroller use has been considered before (e.g.
timer functions, capture and compare, PWM functions
and coprocessor applications).
1.1 F
Users familiar with the PIC16C5X microcontroller family
will realize that this is an enhanced version of the
PIC16C5X architecture. Please refer to Appendix A for
a detailed list of enhancements. Code written for the
PIC16C5X can be easily ported to the PIC16CXXX
family of devices (Appendix B).
1.2 De
PIC16C9XX devices are supported by the complete
line of Microchip Development tools.
Please refer to Section 16.0 for more details about
Microchip’s development tools.
amily and Upward Compatibility
velopment Support
1997 Microchip Technology Inc. DS30444E- page 5
PIC16C9XX
TABLE 1-1: PIC16C9XX FAMILY OF DEVICES
PIC16C923
Clock
Memory
Peripherals
Features
All PICmicro Family devices ha v e Power-on Reset, selectable Watchdog Timer, selectable code protect and high I/O current capability . All PIC16C9XX Family devices use serial programming with clock pin RB6 and data pin RB7.
Maximum Frequency of Operation (MHz) 8 8
EPROM Program Memory 4K 4K
Data Memory (bytes) 176 176
Timer Module(s) TMR0,
TMR1,
TMR2
Capture/Compare/PWM Module(s) 1 1
Serial Port(s)
2
(SPI/I
C, USART)
Parallel Slave Port — —
A/D Converter (8-bit) Channels — 5
LCD Module 4 Com,
Interrupt Sources 8 9
I/O Pins 25 25
Input Pins 27 27
Voltage Range (Volts) 2.5-6.0 2.5-6.0
In-Circuit Serial Programming Yes Yes
Brown-out Reset — —
Packages 64-pin SDIP,
2
SPI/I
C SPI/I
32 Seg
TQFP;
68-pin PLCC,
Die
PIC16C924
TMR0,
TMR1,
TMR2
2
C
4 Com,
32 Seg
64-pin SDIP,
TQFP;
68-pin PLCC,
Die
DS30444E - page 6
1997 Microchip Technology Inc.
PIC16C9XX
2.0 PIC16C9XX DEVICE VARIETIES
A variety of frequency ranges and packaging options
are available . Depending on application and production
requirements, the proper device option can be selected
using the information in the PIC16C9XX Product Identification System section at the end of this data sheet.
When placing orders, please use that page of the data
sheet to specify the correct part number.
For the PIC16C9XX family, there are two device “types”
as indicated in the device number:
1. C , as in PIC16 C 924. These devices have
EPROM type memory and operate over the
standard voltage range.
2. LC , as in PIC16 LC 924. These devices have
EPROM type memory and operate over an
extended voltage range.
2.1 UV Erasab
The UV erasable version, offered in CERQUAD package, is optimal for prototype dev elopment and pilot programs.
The UV erasable version can be erased and reprogrammed to any of the configuration modes.
Microchip's PICSTART
grammers both support the PIC16C9XX. Third party
programmers also are available; refer to the
Third Party Guide
le Devices
Plus and PRO MATE
for a list of sources.
II pro-
Microchip
2.3 Quic
k-Turnaround-Production (QTP)
Devices
Microchip offers a QTP Programming Service for factory production orders. This service is made available
for users who choose not to program a medium to high
quantity of units and whose code patterns have stabilized. The devices are identical to the OTP devices but
with all EPROM locations and configuration options
already programmed by the factory. Certain code and
prototype verification procedures apply before production shipments are available. Please contact your local
Microchip Technology sales office for more details.
2.4 Serializ
Production (SQTP
Microchip offers a unique programming service where
a few user-defined locations in each device are programmed with different serial numbers. The serial numbers may be random, pseudo-random or sequential.
Serial programming allows each device to have a
unique number which can serve as an entry-code,
password or ID number.
ed Quick-Turnaround
SM
) De
vices
2.2 One-Time-Pr
ogrammable (OTP)
Devices
The availability of OTP devices is especially useful for
customers who need the flexibility for frequent code
updates and small volume applications.
The OTP devices , packaged in plastic packages, permit
the user to program them once. In addition to the program memory, the configuration bits must also be programmed.
1997 Microchip Technology Inc. DS30444E - page 7
PIC16C9XX
NOTES:
DS30444E - page 8
1997 Microchip Technology Inc.
PIC16C9XX
3.0 ARCHITECTURAL OVERVIEW
The high performance of the PIC16CXXX family can be
attributed to a number of architectural features commonly found in RISC microprocessors. To begin with,
the PIC16CXXX uses a Harvard architecture, in which,
program and data are accessed from separate memories using separate buses. This improves bandwidth
over traditional von Neumann architecture where program and data are fetched from the same memory
using the same bus. Separating program and data
buses further allows instructions to be sized differently
than the 8-bit wide data word. Instruction opcodes are
14-bits wide making it possible to have all single word
instructions. A 14-bit wide progr am memory access bus
fetches a 14-bit instruction in a single cycle. A
two-stage pipeline overlaps fetch and execution of
instructions (Example 3-1). Consequently, all instructions execute in a single cycle (500 ns @ 8 MHz) e xcept
for program branches.
The PIC16C923 and PIC16C924 both address 4K x 14
of program memory and 176 x 8 of data memory.
The PIC16CXXX can directly or indirectly address its
register files or data memory. All special function registers, including the program counter, are mapped in the
data memory. The PIC16CXXX has an orthogonal
(symmetrical) instruction set that makes it possible to
carry out any operation on any register using any
addressing mode. This symmetrical nature and lack of
‘special optimal situations’ make programming with the
PIC16CXXX simple yet efficient, thus significantly
reducing the learning curve.
PIC16CXXX devices contain an 8-bit ALU and working
register. The ALU is a general purpose ar ithmetic unit.
It performs arithmetic and Boolean functions between
the data in the working register and any register file.
The ALU is 8-bits wide and capable of addition, subtraction, shift and logical operations. Unless otherwise
mentioned, arithmetic operations are two's complement in nature. In two-operand instructions, typically
one operand is the working register (W register). The
other operand is a file register or an immediate constant. In single operand instructions, the operand is
either the W register or a file register.
The W register is an 8-bit working register used f or ALU
operations. It is not an addressable register.
Depending on the instruction executed, the ALU may
affect the values of the Carry (C), Digit Carry (DC), and
Zero (Z) bits in the STATUS register. The C and DC bits
operate as a borro
respectively, in subtraction. See the SUBLW and SUBWF
instructions for examples.
w bit and a digit borrow out bit,
1997 Microchip Technology Inc. DS30444E - page 9
PIC16C9XX
FIGURE 3-1: PIC16C923 BLOCK DIAGRAM
Program
Bus
OSC1/CLKIN
OSC2/CLKOUT
EPROM
Program
Memory
4K x 14
14
Instruction reg
Instruction
Decode &
Control
Timing
Generation
13
Program Counter
8 Level Stack
Direct Addr
8
Power-up
Oscillator
Start-up Timer
Power-on
Watchdog
MCLR
(13-bit)
Timer
Reset
Timer
VDD, VSS
RAM Addr
7
8
Data Bus
RAM
File
Registers
176 x 8
Addr MUX
FSR reg
STATUS reg
3
ALU
W reg
9
MUX
Indirect
8
8
Addr
PORTA
PORTB
PORTC
PORTD
PORTE
RA0
RA1
RA2
RA3
RA4/T0CKI
RA5/SS
RB0/INT
RB1-RB7
RC0/T1OSO/T1CKI
RC1/T1OSI
RC2/CCP1
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
RD0-RD4/SEGnn
RD5-RD7/SEGnn/COMn
Timer0
Synchronous
Serial Port
Timer1, Timer2,
CCP1
LCD
PORTF
PORTG
RE0-RE7/SEGnn
RF0-RF7/SEGnn
RG0-RG7/SEGnn
COM0
VLCD1
VLCD2
LCD3
V
C1
C2
VLCDADJ
DS30444E - page 10
1997 Microchip Technology Inc.
FIGURE 3-2: PIC16C924 BLOCK DIAGRAM
PIC16C9XX
Program
Bus
OSC1/CLKIN
OSC2/CLKOUT
EPROM
Program
Memory
4K x 14
14
Instruction reg
Instruction
Decode &
Control
Timing
Generation
13
Program Counter
8 Level Stack
Direct Addr
8
Power-up
Oscillator
Start-up Timer
Power-on
Watchdog
MCLR
(13-bit)
Timer
Reset
Timer
VDD, VSS
RAM Addr
7
8
Data Bus
RAM
File
Registers
176 x 8
Addr MUX
FSR reg
STATUS reg
3
ALU
W reg
9
MUX
Indirect
8
8
Addr
PORTA
PORTB
PORTC
PORTD
PORTE
RA0/AN0
RA1/AN1
RA2/AN2
RA3/AN3/VREF
RA4/T0CKI
RA5/AN4/SS
RB0/INT
RB1-RB7
RC0/T1OSO/T1CKI
RC1/T1OSI
RC2/CCP1
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
RD0-RD4/SEGnn
RD5-RD7/SEGnn/COMn
Timer0
A/D
Synchronous
Serial Port
Timer1, Timer2,
CCP1
LCD
PORTF
PORTG
RE0-RE7/SEGnn
RF0-RF7/SEGnn
RG0-RG7/SEGnn
COM0
VLCD1
VLCD2
LCD3
V
C1
C2
VLCDADJ
1997 Microchip Technology Inc. DS30444E - page 11
PIC16C9XX
TABLE 3-1: PIC16C9XX PINOUT DESCRIPTION
DIP
Pin Name
OSC1/CLKIN 22 24 14 I ST/CMOS Oscillator crystal input or external clock source input. This
OSC2/CLKOUT 23 25 15 O — Oscillator crystal output. Connects to crystal or resonator
MCLR/VPP 1 2 57 I/P ST Master clear (reset) input or programming voltage input.
RA0/AN0 4 5 60 I/O TTL RA0 can also be Analog input0.
RA1/AN1 5 6 61 I/O TTL RA1 can also be Analog input1.
RA2/AN2 7 8 63 I/O TTL RA2 can also be Analog input2.
RA3/AN3/VREF 8 9 64 I/O TTL RA3 can also be Analog input3 or A/D Voltage Refer-
RA4/T0CKI 9 10 1 I/O ST RA4 can also be the clock input to the Timer0
RA5/AN4/SS 10 11 2 I/O TTL RA5 can be the slave select for the synchronous serial
RB0/INT 12 13 4 I/O TTL/ST RB0 can also be the external interrupt pin. This buffer
RB1 11 12 3 I/O TTL
RB2 3 4 59 I/O TTL
RB3 2 3 58 I/O TTL
RB4 64 68 56 I/O TTL Interrupt on change pin.
RB5 63 67 55 I/O TTL Interrupt on change pin.
RB6 61 65 53 I/O TTL/ST Interrupt on change pin. Serial programming clock.
RB7 62 66 54 I/O TTL/ST Interrupt on change pin. Serial programming data.
RC0/T1OSO/T1CKI 24 26 16 I/O ST RC0 can also be the Timer1 oscillator output or
RC1/T1OSI 25 27 17 I/O ST RC1 can also be the Timer1 oscillator input.
RC2/CCP1 26 28 18 I/O ST RC2 can also be the Capture1 input/Compare1 out-
RC3/SCK/SCL 13 14 5 I/O ST RC3 can also be the synchronous serial clock
RC4/SDI/SDA 14 15 6 I/O ST RC4 can also be the SPI Data In (SPI mode) or data
RC5/SDO 15 16 7 I/O ST RC5 can also be the SPI Data Out (SPI mode).
C1 16 17 8 P LCD Voltage Generation.
C2 17 18 9 P LCD Voltage Generation.
Legend: I = input O = output P = power L = LCD Driver
— = Not used TTL = TTL input ST = Schmitt Trigger input
Pin#
PLCC
Pin#
TQFP
Pin#
Pin
Type
Buffer
Type
Description
buffer is a Schmitt Trigger input when configured in RC
oscillator mode and a CMOS input otherwise.
in crystal oscillator mode. In RC mode, OSC2 pin outputs
CLKOUT which has 1/4 the frequency of OSC1, and
denotes the instruction cycle rate.
This pin is an active low reset to the device.
PORTA is a bi-directional I/O port. The AN and VREF multi-
plexed functions are used by the PIC16C924 only.
ence.
timer/counter. Output is open drain type.
port or Analog input4.
PORTB is a bi-directional I/O port. PORTB can be softw are
programmed for internal weak pull-ups on all inputs.
is a Schmitt Trigger input when configured as an external interrupt.
This buffer is a Schmitt Trigger input when used in
serial programming mode.
This buffer is a Schmitt Trigger input when used in
serial programming mode.
PORTC is a bi-directional I/O port.
Timer1 clock input.
put/PWM1 output.
2
input/output for both SPI and I
I/O (I2C mode).
C modes.
DS30444E - page 12 1997 Microchip Technology Inc.
PIC16C9XX
TABLE 3-1: PIC16C9XX PINOUT DESCRIPTION (Cont.’d)
DIP
Pin Name
COM0 59 63 51 L Common Driver0
RD0/SEG00 29 31 21 I/O/L ST
RD1/SEG01 30 32 22 I/O/L ST
RD2/SEG02 31 33 23 I/O/L ST
RD3/SEG03 32 34 24 I/O/L ST
RD4/SEG04 33 35 25 I/O/L ST
RD5/SEG29/COM3 56 60 48 I/L ST
RD6/SEG30/COM2 57 61 49 I/L ST
RD7/SEG31/COM1 58 62 50 I/L ST
RE0/SEG05 34 37 26 I/L ST
RE1/SEG06 35 38 27 I/L ST
RE2/SEG07 36 39 28 I/L ST
RE3/SEG08 37 40 29 I/L ST
RE4/SEG09 38 41 30 I/L ST
RE5/SEG10 39 42 31 I/L ST
RE6/SEG11 40 43 32 I/L ST
RE7/SEG27 - 36 - I/L ST
RF0/SEG12 41 44 33 I/L ST
RF1/SEG13 42 45 34 I/L ST
RF2/SEG14 43 46 35 I/L ST
RF3/SEG15 44 47 36 I/L ST
RF4/SEG16 45 48 37 I/L ST
RF5/SEG17 46 49 38 I/L ST
RF6/SEG18 47 50 39 I/L ST
RF7/SEG19 48 51 40 I/L ST
RG0/SEG20 49 53 41 I/L ST
RG1/SEG21 50 54 42 I/L ST
RG2/SEG22 51 55 43 I/L ST
RG3/SEG23 52 56 44 I/L ST
RG4/SEG24 53 57 45 I/L ST
RG5/SEG25 54 58 46 I/L ST
RG6/SEG26 55 59 47 I/L ST
RG7/SEG28 — 52 — I/L ST
VLCDADJ 28 30 20 P LCD Voltage Generation.
VDD — 21 — P Analog Power (PIC16C924 only).
A
VDD — 21 — P Power (PIC16C923 only).
VLCD1 27 29 19 P LCD Voltage.
VLCD2 18 19 10 P — LCD Voltage.
Legend: I = input O = output P = power L = LCD Driver
— = Not used TTL = TTL input ST = Schmitt Trigger input
Pin#
PLCC
Pin#
TQFP
Pin#
Pin
Type
Buffer
Type
Description
PORTD is a digital input/output port. These pins are also
used as LCD Segment and/or Common Drivers.
Segment Driver00/Digital Input/Output.
Segment Driver01/Digital Input/Output.
Segment Driver02/Digital Input/Output.
Segment Driver03/Digital Input/Output.
Segment Driver04/Digital Input/Output.
Segment Driver29/Common Driver3/Digital Input.
Segment Driver30/Common Driver2/Digital Input.
Segment Driver31/Common Driver1/Digital Input.
PORTE is a digital input or LCD Segment Driver port.
Segment Driver05.
Segment Driver06.
Segment Driver07.
Segment Driver08.
Segment Driver09.
Segment Driver10.
Segment Driver11.
Segment Driver27 (Not available on 64-pin devices).
PORTF is a digital input or LCD Segment Driver port.
Segment Driver12.
Segment Driver13.
Segment Driver14.
Segment Driver15.
Segment Driver16.
Segment Driver17.
Segment Driver18.
Segment Driver19.
PORTG is a digital input or LCD Segment Driver port.
Segment Driver20.
Segment Driver21.
Segment Driver22.
Segment Driver23.
Segment Driver24.
Segment Driver25.
Segment Driver26.
Segment Driver28 (Not available on 64-pin devices).
1997 Microchip Technology Inc. DS30444E - page 13
PIC16C9XX
TABLE 3-1: PIC16C9XX PINOUT DESCRIPTION (Cont.’d)
DIP
Pin Name
VLCD3 19 20 11 P — LCD Voltage.
VDD 20, 60 22, 64 12, 52 P — Digital power.
VSS 6, 21 7, 23 13, 62 P — Ground reference.
NC — 1 — — — These pins are not internally connected. These pins should
Legend: I = input O = output P = power L = LCD Driver
— = Not used TTL = TTL input ST = Schmitt Trigger input
Pin#
PLCC
Pin#
TQFP
Pin#
Pin
Type
Buffer
Type
Description
be left unconnected.
DS30444E - page 14 1997 Microchip Technology Inc.
PIC16C9XX
3.1 Clocking Scheme/Instruction Cycle
The clock input (from OSC1) is internally divided by
four to generate four non-overlapping quadrature
clocks namely Q1, Q2, Q3 and Q4. Internally, the program counter (PC) is incremented every Q1, the
instruction is fetched from the program memory and
latched into the instruction register in Q4. The instruction is decoded and executed during the following Q1
through Q4. The clocks and instruction execution flow
is shown in Figure 3-3.
FIGURE 3-3: CLOCK/INSTRUCTION CYCLE
Q2 Q3 Q4
OSC1
Q1
Q2
Q3
Q4
PC
OSC2/CLKOUT
(RC mode)
Q1
PC PC+1 PC+2
Fetch INST (PC)
Execute INST (PC-1) Fetch INST (PC+1)
Q1
3.2 Instruction Flow/Pipelining
An “Instruction Cycle” consists of four Q cycles (Q1,
Q2, Q3 and Q4). The instruction fetch and execute are
pipelined such that fetch takes one instruction cycle
while decode and execute takes another instruction
cycle. However, due to the pipelining, each instruction
effectively executes in one cycle. If an instruction
causes the program counter to change (e.g. GOTO)
then two cycles are required to complete the instruction
(Example 3-1).
A fetch cycle begins with the program counter (PC)
incrementing in Q1.
In the execution cycle , the fetched instruction is latched
into the “Instruction Register" in cycle Q1. This instruction is then decoded and executed during the Q2, Q3,
and Q4 cycles. Data memory is read during Q2 (operand read) and written during Q4 (destination write).
Q2 Q3 Q4
Execute INST (PC) Fetch INST (PC+2)
Q2 Q3 Q4
Q1
Execute INST (PC+1)
Internal
phase
clock
EXAMPLE 3-1: INSTRUCTION PIPELINE FLOW
Tcy0 Tcy1 Tcy2 Tcy3 Tcy4 Tcy5
1. MOVLW 55h
2. MOVWF PORTB
3. CALL SUB_1
4. BSF PORTA, BIT3 (Forced NOP)
5. Instruction @ address SUB_1
All instructions are single cycle, except for any program branches. These take two cycles since the fetch
instruction is “flushed” from the pipeline while the new instruction is being fetched and then executed.
1997 Microchip Technology Inc. DS30444E - page 15
Fetch 1 Execute 1
Fetch 2 Execute 2
Fetch 3 Execute 3
Fetch 4 Flush
Fetch SUB_1 Execute SUB_1
PIC16C9XX
NOTES:
DS30444E - page 16 1997 Microchip Technology Inc.
PIC16C9XX
4.0 MEMORY ORGANIZATION
4.1 Program Memory Organization
The PIC16C9XX family has a 13-bit program counter
capable of addressing an 8K x 14 program memory
space.
Only the first 4K x 14 (0000h-0FFFh) is physically
implemented. Accessing a location above the physically implemented addresses will cause a wraparound.
The reset vector is at 0000h and the interrupt vector is
at 0004h.
FIGURE 4-1: PROGRAM MEMORY MAP
AND STACK
PC<12:0>
CALL, RETURN
RETFIE, RETLW
Interrupt Vector
On-chip Program
Space
User Memory
Memory (Page 0)
On-chip Program
Memory (Page 1)
Stack Level 1
Stack Level 8
Reset Vector
13
0000h
0004h
0005h
07FFh
0800h
4.2 Data Memory Organization
The data memory is partitioned into four Banks which
contain the General Purpose Registers and the Special
Function Registers. Bits RP1 and RP0 are the bank
select bits.
RP1:RP0 (STATUS<6:5>)
11 = Bank 3 (180h-1FFh)
10 = Bank 2 (100h-17Fh)
01 = Bank 1 (80h-FFh)
00 = Bank 0 (00h-7Fh)
The lower locations of each Bank are reserved for the
Special Function Registers. Above the Special Function Registers are General Purpose Registers implemented as static RAM. All four banks contain special
function registers. Some “high use” special function
registers are mirrored in other banks for code reduction
and quicker access.
4.2.1 GENERAL PURPOSE REGISTER FILE
The register file can be accessed either directly , or indi-
rectly through the File Select Register FSR
(Section 4.5).
The following General Purpose Registers are not physically implemented:
• F0h-FFh of Bank 1
• 170h-17Fh of Bank 2
• 1F0h-1FFh of Bank 3
These locations are used for common access across
banks.
0FFFh
1000h
1FFFh
1997 Microchip Technology Inc. DS30444E - page 17
PIC16C9XX
FIGURE 4-2: REGISTER FILE MAP
File
Address
Indirect addr.
TMR0
PCL
STATUS
FSR
PORTA
PORTB
PORTC
PORTD
PORTE
PCLATH
INTCON
PIR1
TMR1L
TMR1H
T1CON
TMR2
T2CON
SSPBUF
SSPCON
CCPR1L
CCPR1H
CCP1CON
ADRES
(2)
ADCON0
(2)
(1)
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
10h
11h
12h
13h
14h
15h
16h
17h
18h
19h
1Ah
1Bh
1Ch
1Dh
1Eh
1Fh
20h
Indirect addr.
OPTION
PCL
STATUS
FSR
TRISA
TRISB
TRISC
TRISD
TRISE
PCLATH
INTCON
PIE1
PCON
PR2
SSPADD
SSPSTAT
ADCON1
(2)
(1)
File
Address
80h
81h
82h
83h
84h
85h
86h
87h
88h
89h
8Ah
8Bh
8Ch
8Dh
8Eh
8Fh
90h
91h
92h
93h
94h
95h
96h
97h
98h
99h
9Ah
9Bh
9Ch
9Dh
9Eh
9Fh
A0h
Indirect addr.
TMR0
PCL
STATUS
FSR
PORTB
PORTF
PORTG
PCLATH
INTCON
LCDSE
LCDPS
LCDCON
LCDD00
LCDD01
LCDD02
LCDD03
LCDD04
LCDD05
LCDD06
LCDD07
LCDD08
LCDD09
LCDD10
LCDD11
LCDD12
LCDD13
LCDD14
LCDD15
(1)
File
Address
100h
101h
102h
103h
104h
105h
106h
107h
108h
109h
10Ah
10Bh
10Ch
10Dh
10Eh
10Fh
110h
111h
112h
113h
114h
115h
116h
117h
118h
119h
11Ah
11Bh
11Ch
11Dh
11Eh
11Fh
120h
Indirect addr.
OPTION
PCL
STATUS
FSR
TRISB
TRISF
TRISG
PCLATH
INTCON
Address
(1)
File
180h
181h
182h
183h
184h
185h
186h
187h
188h
189h
18Ah
18Bh
18Ch
18Dh
18Eh
18Fh
190h
191h
192h
193h
194h
195h
196h
197h
198h
199h
19Ah
19Bh
19Ch
19Dh
19Eh
19Fh
1A0h
General
Purpose
General
Register
Purpose
Register
Mapped in
Bank 0
Bank 0
7Fh
DS30444E - page 18 1997 Microchip Technology Inc.
70h-7Fh
Bank 1
Unimplemented data memory locations, read as '0'.
Note 1: Not a physical register.
2: These registers are not implemented on the PIC16C923.
EFh
F0h
FFh
Mapped in
Bank 0
70h-7Fh
Bank 2
16F
170
17F
Mapped in
Bank 0
70h-7Fh
Bank 3
1EFh
1F0h
1FFh
PIC16C9XX
4.2.2 SPECIAL FUNCTION REGISTERS
The special function registers can be classified into two
sets (core and peripheral). Those registers associated
The Special Function Registers are registers used by
the CPU and Peripheral Modules for controlling the
desired operation of the device. These registers are
implemented as static RAM.
with the “core” functions are described in this section,
and those related to the operation of the peripheral features are described in the section of that peripheral feature.
T ABLE 4-1: SPECIAL FUNCTION REGISTER SUMMARY
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Value on
Power-on
Reset
Bank 0
00h INDF Addressing this location uses contents of FSR to address data memory (not a physical register) 0000 0000 0000 0000
01h TMR0 Timer0 module’s register xxxx xxxx uuuu uuuu
02h PCL Program Counter's (PC) Least Significant Byte 0000 0000 0000 0000
03h STATUS IRP RP1 RP0 T
04h FSR Indirect data memory address pointer xxxx xxxx uuuu uuuu
05h PORTA
06h PORTB PORTB Data Latch when written: PORTB pins when read xxxx xxxx uuuu uuuu
07h PORTC
08h PORTD PORTD Data Latch when written: PORTD pins when read 0000 0000 0000 0000
09h PORTE PORTE pins when read 0000 0000 0000 0000
0Ah PCLATH
0Bh INTCON GIE PEIE T0IE INTE RBIE T0IF INTF RBIF 0000 000x 0000 000u
0Ch PIR1 LCDIF ADIF
0Dh — Unimplemented — —
0Eh TMR1L Holding register for the Least Significant Byte of the 16-bit TMR1 register xxxx xxxx uuuu uuuu
0Fh TMR1H Holding register for the Most Significant Byte of the 16-bit TMR1 register xxxx xxxx uuuu uuuu
10h T1CON
11h TMR2 Timer2 module’s register 0000 0000 0000 0000
12h T2CON
13h SSPBUF Synchronous Serial Port Receive Buffer/Transmit Register xxxx xxxx uuuu uuuu
14h SSPCON WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 0000 0000
15h CCPR1L Capture/Compare/PWM Register (LSB) xxxx xxxx uuuu uuuu
16h CCPR1H Capture/Compare/PWM Register (MSB) xxxx xxxx uuuu uuuu
17h CCP1CON
18h — Unimplemented — —
19h — Unimplemented — —
1Ah — Unimplemented — —
1Bh — Unimplemented — —
1Ch — Unimplemented — —
1Dh — Unimplemented — —
(1)
1Eh
1Fh
Legend: x = unknown, u = unchanged, q = value depends on condition, - = unimplemented read as '0',
Note 1: Registers ADRES, ADCON0, and ADCON1 are not implemented in the PIC16C923, read as '0'.
ADRES A/D Result Register xxxx xxxx uuuu uuuu
(1)
ADCON0 ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE
shaded locations are unimplemented, read as ‘0’.
2: These bits are reserved on the PIC16C923, always maintain these bits clear.
3: These pixels do not display, but can be used as general purpose RAM.
4: PIC16C923 reset values for PORTA: --xx xxxx for a POR, and --uu uuuu for all other resets,
PIC16C924 reset values for PORTA: --0x 0000 when read.
5: Bit1 of ADCON0 is reserved on the PIC16C924, always maintain this bit clear.
— — PORTA Data Latch when written: PORTA pins when read
— — PORTC Data Latch when written: PORTC pins when read --xx xxxx --uu uuuu
— — — Write Buffer for the upper 5 bits of the Program Counter ---0 0000 ---0 0000
(2)
— — T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON --00 0000 --uu uuuu
— TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 -000 0000
— — CCP1X CCP1Y CCP1M3 CCP1M2 CCP1M1 CCP1M0 --00 0000 --00 0000
— — SSPIF CCP1IF TMR2IF TMR1IF 00-- 0000 00-- 0000
O PD Z DC C 0001 1xxx 000q quuu
(4) (4)
(5)
ADON 0000 0000 0000 0000
Value on all
other resets
1997 Microchip Technology Inc. DS30444E - page 19
PIC16C9XX
TABLE 4-1: SPECIAL FUNCTION REGISTER SUMMARY (Cont.’d)
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Bank 1
80h INDF Addressing this location uses contents of FSR to address data memory (not a physical register) 0000 0000 0000 0000
81h OPTION RBPU
82h PCL Program Counter's (PC) Least Significant Byte 0000 0000 0000 0000
83h STATUS IRP RP1 RP0 T
84h FSR Indirect data memory address pointer xxxx xxxx uuuu uuuu
85h TRISA
86h TRISB PORTB Data Direction Register 1111 1111 1111 1111
87h TRISC
88h TRISD PORTD Data Direction Register 1111 1111 1111 1111
89h TRISE PORTE Data Direction Register 1111 1111 1111 1111
8Ah PCLATH
8Bh INTCON GIE PEIE T0IE INTE RBIE T0IF INTF RBIF 0000 000x 0000 000u
8Ch PIE1 LCDIE ADIE
8Dh — Unimplemented — —
8Eh PCON
8Fh — Unimplemented — —
90h — Unimplemented — —
91h — Unimplemented — —
92h PR2 Timer2 Period Register 1111 1111 1111 1111
93h SSPADD Synchronous Serial Port (I
94h SSPSTAT SMP CKE D/A
95h — Unimplemented — —
96h — Unimplemented — —
97h — Unimplemented — —
98h — Unimplemented — —
99h — Unimplemented — —
9Ah — Unimplemented — —
9Bh — Unimplemented — —
9Ch — Unimplemented — —
9Dh — Unimplemented — —
9Eh — Unimplemented — —
(1)
9Fh
Legend: x = unknown, u = unchanged, q = value depends on condition, - = unimplemented read as '0',
Note 1: Registers ADRES, ADCON0, and ADCON1 are not implemented in the PIC16C923, read as '0'.
ADCON1 — — — — — PCFG2 PCFG1 PCFG0 ---- -000 ---- -000
shaded locations are unimplemented, read as ‘0’.
2: These bits are reserved on the PIC16C923, always maintain these bits clear.
3: These pixels do not display, but can be used as general purpose RAM.
4: PIC16C923 reset values for PORTA: --xx xxxx for a POR, and --uu uuuu for all other resets,
PIC16C924 reset values for PORTA: --0x 0000 when read.
5: Bit1 of ADCON0 is reserved on the PIC16C924, always maintain this bit clear.
INTEDG T0CS T0SE PSA PS2 PS1 PS0 1111 1111 1111 1111
O PD Z DC C 0001 1xxx 000q quuu
— — PORTA Data Direction Register --11 1111 --11 1111
— — PORTC Data Direction Register --11 1111 --11 1111
— — — Write Buffer for the upper 5 bits of the PC ---0 0000 ---0 0000
(2)
— — — — — — POR — ---- --0- ---- --u-
— — SSPIE CCP1IE TMR2IE TMR1IE 00-- 0000 00-- 0000
2
C mode) Address Register 0000 0000 0000 0000
P S R/W UA BF 0000 0000 0000 0000
Value on
Power-on
Reset
Value on all
other resets
DS30444E - page 20 1997 Microchip Technology Inc.
PIC16C9XX
TABLE 4-1: SPECIAL FUNCTION REGISTER SUMMARY (Cont.’d)
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Bank 2
100h INDF Addressing this location uses contents of FSR to address data memory (not a physical register) 0000 0000 0000 0000
101h TMR0 Timer0 module’s register xxxx xxxx uuuu uuuu
102h PCL Program Counter's (PC) Least Significant Byte 0000 0000 0000 0000
103h STATUS IRP RP1 RP0 T
104h FSR Indirect data memory address pointer xxxx xxxx uuuu uuuu
105h — Unimplemented — —
106h PORTB PORTB Data Latch when written: PORTB pins when read xxxx xxxx uuuu uuuu
107h PORTF PORTF pins when read 0000 0000 0000 0000
108h PORTG PORTG pins when read 0000 0000 0000 0000
109h — Unimplemented — —
10Ah PCLATH
10Bh INTCON GIE PEIE T0IE INTE RBIE T0IF INTF RBIF 0000 000x 0000 000u
10Ch — Unimplemented — —
10Dh LCDSE SE29 SE27 SE20 SE16 SE12 SE9 SE5 SE0 1111 1111 1111 1111
10Eh LCDPS
10Fh LCDCON LCDEN SLPEN
110h LCDD00
111h LCDD01
112h LCDD02
113h LCDD03
114h LCDD04
115h LCDD05
116h LCDD06
117h LCDD07
118h LCDD08
119h LCDD09
11Ah LCDD10
11Bh LCDD11
11Ch LCDD12
11Dh LCDD13
11Eh LCDD14
11Fh LCDD15
Legend: x = unknown, u = unchanged, q = value depends on condition, - = unimplemented read as '0',
shaded locations are unimplemented, read as ‘0’.
Note 1: Registers ADRES, ADCON0, and ADCON1 are not implemented in the PIC16C923, read as '0'.
2: These bits are reserved on the PIC16C923, always maintain these bits clear.
3: These pixels do not display, but can be used as general purpose RAM.
4: PIC16C923 reset values for PORTA: --xx xxxx for a POR, and --uu uuuu for all other resets,
PIC16C924 reset values for PORTA: --0x 0000 when read.
5: Bit1 of ADCON0 is reserved on the PIC16C924, always maintain this bit clear.
— — — Write Buffer for the upper 5 bits of the PC ---0 0000 ---0 0000
— — — — LP3 LP2 LP1 LP0 ---- 0000 ---- 0000
— VGEN CS1 CS0 LMUX1 LMUX0 00-0 0000 00-0 0000
SEG07
COM0
SEG15
COM0
SEG23
COM0
SEG31
COM0
SEG07
COM1
SEG15
COM1
SEG23
COM1
SEG31
COM1
SEG07
COM2
SEG15
COM2
SEG23
COM2
SEG31
COM2
SEG07
COM3
SEG15
COM3
SEG23
COM3
SEG31
COM3
SEG06
COM0
SEG14
COM0
SEG22
COM0
SEG30
COM0
SEG06
COM1
SEG14
COM1
SEG22
COM1
SEG30
(3)
COM1
SEG06
COM2
SEG14
COM2
SEG22
COM2
SEG30
(3)
COM2
SEG06
COM3
SEG14
COM3
SEG22
COM3
SEG30
(3)
COM3
SEG05
COM0
SEG13
COM0
SEG21
COM0
SEG29
COM0
SEG05
COM1
SEG13
COM1
SEG21
COM1
SEG29
COM1
SEG05
COM2
SEG13
COM2
SEG21
COM2
SEG29
(3)
COM2
SEG05
COM3
SEG13
COM3
SEG21
COM3
SEG29
(3)
COM3
(3)
O PD Z DC C 0001 1xxx 000q quuu
SEG04
COM0
SEG12
COM0
SEG20
COM0
SEG28
COM0
SEG04
COM1
SEG12
COM1
SEG20
COM1
SEG28
COM1
SEG04
COM2
SEG12
COM2
SEG20
COM2
SEG28
COM2
SEG04
COM3
SEG12
COM3
SEG20
COM3
SEG28
COM3
SEG03
COM0
SEG11
COM0
SEG19
COM0
SEG27
COM0
SEG03
COM1
SEG11
COM1
SEG19
COM1
SEG27
COM1
SEG03
COM2
SEG11
COM2
SEG19
COM2
SEG27
COM2
SEG03
COM3
SEG11
COM3
SEG19
COM3
SEG27
COM3
SEG02
COM0
SEG10
COM0
SEG18
COM0
SEG26
COM0
SEG02
COM1
SEG10
COM1
SEG18
COM1
SEG26
COM1
SEG02
COM2
SEG10
COM2
SEG18
COM2
SEG26
COM2
SEG02
COM3
SEG10
COM3
SEG18
COM3
SEG26
COM3
SEG01
COM0
SEG09
COM0
SEG17
COM0
SEG25
COM0
SEG01
COM1
SEG09
COM1
SEG17
COM1
SEG25
COM1
SEG01
COM2
SEG09
COM2
SEG17
COM2
SEG25
COM2
SEG01
COM3
SEG09
COM3
SEG17
COM3
SEG25
COM3
SEG00
COM0
SEG08
COM0
SEG16
COM0
SEG24
COM0
SEG00
COM1
SEG08
COM1
SEG16
COM1
SEG24
COM1
SEG00
COM2
SEG08
COM2
SEG16
COM2
SEG24
COM2
SEG00
COM3
SEG08
COM3
SEG16
COM3
SEG24
COM3
Value on
Power-on
Reset
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
Value on all
other resets
1997 Microchip Technology Inc. DS30444E - page 21
PIC16C9XX
TABLE 4-1: SPECIAL FUNCTION REGISTER SUMMARY (Cont.’d)
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Bank 3
180h INDF Addressing this location uses contents of FSR to address data memory (not a physical register) 0000 0000 0000 0000
181h OPTION RBPU
182h PCL Program Counter's (PC) Least Significant Byte 0000 0000 0000 0000
183h STATUS IRP RP1 RP0 T
184h FSR Indirect data memory address pointer xxxx xxxx uuuu uuuu
185h — Unimplemented — —
186h TRISB PORTB Data Direction Register 1111 1111 1111 1111
187h TRISF PORTF Data Direction Register 1111 1111 1111 1111
188h TRISG PORTG Data Direction Register 1111 1111 1111 1111
189h — Unimplemented — —
18Ah PCLATH
18Bh INTCON GIE PEIE T0IE INTE RBIE T0IF INTF RBIF 0000 000x 0000 000u
18Ch — Unimplemented — —
18Dh — Unimplemented — —
18Eh — Unimplemented — —
18Fh — Unimplemented — —
190h — Unimplemented — —
191h — Unimplemented — —
192h — Unimplemented — —
193h — Unimplemented — —
194h — Unimplemented — —
195h — Unimplemented — —
196h — Unimplemented — —
197h — Unimplemented — —
198h — Unimplemented — —
199h — Unimplemented — —
19Ah — Unimplemented — —
19Bh — Unimplemented — —
19Ch — Unimplemented — —
19Dh — Unimplemented — —
19Eh — Unimplemented — —
19Fh — Unimplemented — —
Legend: x = unknown, u = unchanged, q = value depends on condition, - = unimplemented read as '0',
shaded locations are unimplemented, read as ‘0’.
Note 1: Registers ADRES, ADCON0, and ADCON1 are not implemented in the PIC16C923, read as '0'.
2: These bits are reserved on the PIC16C923, always maintain these bits clear.
3: These pixels do not display, but can be used as general purpose RAM.
4: PIC16C923 reset values for PORTA: --xx xxxx for a POR, and --uu uuuu for all other resets,
PIC16C924 reset values for PORTA: --0x 0000 when read.
5: Bit1 of ADCON0 is reserved on the PIC16C924, always maintain this bit clear.
INTEDG T0CS T0SE PSA PS2 PS1 PS0 1111 1111 1111 1111
O PD Z DC C 0001 1xxx 000q quuu
— — — Write Buffer for the upper 5 bits of the PC ---0 0000 ---0 0000
Value on
Power-on
Reset
Value on all
other resets
DS30444E - page 22 1997 Microchip Technology Inc.
PIC16C9XX
4.2.2.1 STATUS REGISTER
The ST ATUS register, shown in Figure 4-3, contains the
arithmetic status of the ALU, the RESET status and the
bank select bits for data memory.
The STATUS register can be the destination for any
instruction, as with any other register. If the STATUS
register is the destination for an instruction that affects
the Z, DC or C bits, then the write to these three bits is
disabled. These bits are set or cleared according to the
device logic. Furthermore, the T
writable. Therefore, the result of an instruction with the
STATUS register as destination may be different than
intended.
For example, CLRF STATUS will clear the upper-three
bits and set the Z bit. This leaves the STATUS register
as 000u u1uu (where u = unchanged).
O and PD bits are not
It is recommended, therefore, that only BCF, BSF,
SWAPF and MOVWF instructions are used to alter the
STATUS register because these instructions do not
affect the Z, C or DC bits from the STA TUS register. For
other instructions, not affecting any status bits, see the
“Instruction Set Summary.”
Note 1: The C and DC bits operate as a borrow
and digit borrow bit, respectively, in subtraction. See the SUBLW and SUBWF
instructions for examples.
FIGURE 4-3: STATUS REGISTER (ADDRESS 03h, 83h, 103h, 183h)
R/W-0 R/W-0 R/W-0 R-1 R-1 R/W-x R/W-x R/W-x
IRP RP1 RP0 TO PD Z DC C R = Readable bit
bit7 bit0
bit 7: IRP: Register Bank Select bit (used for indirect addressing)
1 = Bank 2, 3 (100h - 1FFh)
0 = Bank 0, 1 (00h - FFh)
bit 6-5: RP1:RP0: Register Bank Select bits (used for direct addressing)
11 = Bank 3 (180h - 1FFh)
10 = Bank 2 (100h - 17Fh)
01 = Bank 1 (80h - FFh)
00 = Bank 0 (00h - 7Fh)
bit 4: T
bit 3: PD
bit 2: Z: Zero bit
bit 1: DC: Digit carry/borro
bit 0: C: Carry/borro
O: Time-out bit
1 = After power-up, CLRWDT instruction, or SLEEP instruction
0 = A WDT time-out occurred
: Power-down bit
1 = After power-up or by the CLRWDT instruction
0 = By execution of the SLEEP instruction
1 = The result of an arithmetic or logic operation is zero
0 = The result of an arithmetic or logic operation is not zero
w bit (ADDWF, ADDLW,SUBLW,SUBWF instructions) (for borrow the polarity is reversed)
1 = A carry-out from the 4th low order bit of the result occurred
0 = No carry-out from the 4th low order bit of the result
w bit (ADDWF, ADDLW,SUBLW,SUBWF instructions) (for borrow the polarity is reversed)
1 = A carry-out from the most significant bit of the result occurred
0 = No carry-out from the most significant bit of the result occurred
Note: A subtraction is executed by adding the two’s complement of the second operand. For rotate (RRF,
RLF) instructions, this bit is loaded with either the high or low order bit of the source register.
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
1997 Microchip Technology Inc. DS30444E - page 23
PIC16C9XX
4.2.2.2 OPTION REGISTER
Note: To achieve a 1:1 prescaler assignment for
The OPTION register is a readable and writable register which contains various control bits to configure the
the TMR0 register, assign the prescaler to
the Watchdog Timer.
TMR0/WDT prescaler, the external RB0/INT pin interrupt, TMR0, and the weak pull-ups on PORTB.
FIGURE 4-4: OPTION REGISTER (ADDRESS 81h, 181h)
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 R = Readable bit
bit7 bit0
bit 7: RBPU: PORTB Pull-up Enable bit
1 = PORTB pull-ups are disabled
0 = PORTB pull-ups are enabled by individual port latch values
bit 6: INTEDG: Interrupt Edge Select bit
1 = Interrupt on rising edge of RB0/INT pin
0 = Interrupt on falling edge of RB0/INT pin
bit 5: T0CS: TMR0 Clock Source Select bit
1 = Transition on RA4/T0CKI pin
0 = Internal instruction cycle clock (CLKOUT)
bit 4: T0SE: TMR0 Source Edge Select bit
1 = Increment on high-to-low transition on RA4/T0CKI pin
0 = Increment on low-to-high transition on RA4/T0CKI pin
bit 3: PSA: Prescaler Assignment bit
1 = Prescaler is assigned to the WDT
0 = Prescaler is assigned to the Timer0 module
bit 2-0: PS2:PS0: Prescaler Rate Select bits
Bit Value TMR0 Rate WDT Rate
000
001
010
011
100
101
110
111
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
1 : 256
1 : 1
1 : 2
1 : 4
1 : 8
1 : 16
1 : 32
1 : 64
1 : 128
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
DS30444E - page 24 1997 Microchip Technology Inc.
PIC16C9XX
4.2.2.3 INTCON REGISTER
The INTCON Register is a readable and writable regis-
ter which contains various enable and flag bits for the
TMR0 register overflow, RB Port change and external
RB0/INT pin interrupts.
Note: Interrupt flag bits get set when an interrupt
condition occurs regardless of the state of
its corresponding enable bit or the global
enable bit, GIE (INTCON<7>).
FIGURE 4-5: INTCON REGISTER (ADDRESS 0Bh, 8Bh, 10Bh, 18Bh)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-x
GIE PEIE T0IE INTE RBIE T0IF INTF RBIF R = Readable bit
bit7 bit0
bit 7: GIE: Global Interrupt Enable bit
1 = Enables all un-masked interrupts
0 = Disables all interrupts
bit 6: PEIE: Peripheral Interrupt Enable bit
1 = Enables all un-masked peripheral interrupts
0 = Disables all peripheral interrupts
bit 5: T0IE: TMR0 Overflow Interrupt Enable bit
1 = Enables the TMR0 interrupt
0 = Disables the TMR0 interrupt
bit 4: INTE: RB0/INT External Interrupt Enable bit
1 = Enables the RB0/INT external interrupt
0 = Disables the RB0/INT external interrupt
bit 3: RBIE: RB Port Change Interrupt Enable bit
1 = Enables the RB port change interrupt
0 = Disables the RB port change interrupt
bit 2: T0IF: TMR0 Overflow Interrupt Flag bit
1 = TMR0 register has overflowed (must be cleared in software)
0 = TMR0 register did not overflow
bit 1: INTF: RB0/INT External Interrupt Flag bit
1 = The RB0/INT external interrupt occurred (must be cleared in software)
0 = The RB0/INT external interrupt did not occur
bit 0: RBIF: RB Port Change Interrupt Flag bit
1 = At least one of the RB7:RB4 pins changed state (see Section 5.2 to clear interrupt)
0 = None of the RB7:RB4 pins have changed state
Interrupt flag bits get set when an interrupt condition occurs regardless of the state of its corresponding enable bit or the
global enable bit, GIE (INTCON<7>). User software should ensure the appropriate interrupt flag bits are clear prior to
enabling an interrupt.
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
1997 Microchip Technology Inc. DS30444E - page 25
PIC16C9XX
4.2.2.4 PIE1 REGISTER
Note: Bit PEIE (INTCON<6>) must be set to
This register contains the individual enable bits for the
enable any peripheral interrupt.
peripheral interrupts.
FIGURE 4-6: PIE1 REGISTER (ADDRESS 8Ch)
R/W-0 R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0
LCDIE ADIE
bit7 bit0
bit 7: LCDIE: LCD Interrupt Enable bit
bit 6: ADIE: A/D Converter Interrupt Enable bit
bit 5-4: Unimplemented: Read as '0'
bit 3: SSPIE: Synchronous Serial Port Interrupt Enable bit
bit 2: CCP1IE: CCP1 Interrupt Enable bit
bit 1: TMR2IE: TMR2 to PR2 Match Interrupt Enable bit
bit 0: TMR1IE: TMR1 Overflow Interrupt Enable bit
Note 1: Bit ADIE is reserved on the PIC16C923, always maintain this bit clear.
(1)
— — SSPIE CCP1IE TMR2IE TMR1IE R = Readable bit
1 = Enables the LCD interrupt
0 = Disables the LCD interrupt
(1)
1 = Enables the A/D interrupt
0 = Disables the A/D interrupt
1 = Enables the SSP interrupt
0 = Disables the SSP interrupt
1 = Enables the CCP1 interrupt
0 = Disables the CCP1 interrupt
1 = Enables the TMR2 to PR2 match interrupt
0 = Disables the TMR2 to PR2 match interrupt
1 = Enables the TMR1 overflow interrupt
0 = Disables the TMR1 overflow interrupt
W = Writable bit
U = Unimplemented bit,
read as ‘0’
- n = Value at POR reset
DS30444E - page 26 1997 Microchip Technology Inc.
PIC16C9XX
4.2.2.5 PIR1 REGISTER
This register contains the individual flag bits for the
peripheral interrupts.
Note: Interrupt flag bits get set when an interrupt
condition occurs regardless of the state of
its corresponding enable bit or the global
enable bit, GIE (INTCON<7>). User software should ensure the appropriate interrupt flag bits are clear prior to enabling an
interrupt.
FIGURE 4-7: PIR1 REGISTER (ADDRESS 0Ch)
R/W-0 R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0
LCDIF ADIF
bit7 bit0
bit 7: LCDIF: LCD Interrupt Flag bit
bit 6: ADIF: A/D Converter Interrupt Flag bit
bit 5-4: Unimplemented: Read as '0'
bit 3: SSPIF: Synchronous Serial Port Interrupt Flag bit
bit 2: CCP1IF: CCP1 Interrupt Flag bit
bit 1: TMR2IF: TMR2 to PR2 Match Interrupt Flag bit
bit 0: TMR1IF: TMR1 Overflow Interrupt Flag bit
Note 1: Bit ADIF is reserved on the PIC16C923, always maintain this bit clear.
Interrupt flag bits get set when an interrupt condition occurs regardless of the state of its corresponding enable bit or the
global enable bit, GIE (INTCON<7>). User software should ensure the appropriate interrupt flag bits are clear prior to
enabling an interrupt.
(1)
— — SSPIF CCP1IF TMR2IF TMR1IF R = Readable bit
W = Writable bit
U = Unimplemented bit,
- n = Value at POR reset
1 = LCD interrupt occurred (must be cleared in software)
0 = LCD interrupt did not occur
(1)
1 = An A/D conversion completed (must be cleared in software)
0 = The A/D conversion is not complete
1 = The transmission/reception is complete (must be cleared in software)
0 = Waiting to transmit/receive
Capture Mode
1 = A TMR1 register capture occurred (must be cleared in software)
0 = No TMR1 register capture occurred
Compare Mode
1 = A TMR1 register compare match occurred (must be cleared in software)
0 = No TMR1 register compare match occurred
PWM Mode
Unused in this mode
1 = TMR2 to PR2 match occurred (must be cleared in software)
0 = No TMR2 to PR2 match occurred
1 = TMR1 register overflowed (must be cleared in software)
0 = TMR1 register did not overflow
read as ‘0’
1997 Microchip Technology Inc. DS30444E - page 27
PIC16C9XX
4.2.2.6 PCON REGISTER
The Power Control (PCON) register contains a flag bit
to allow differentiation between a Power-on Reset
(POR) to an external MCLR
Reset or WDT Reset.
For various reset conditions see Table 14-4 and
Table 14-5.
FIGURE 4-8: PCON REGISTER (ADDRESS 8Eh)
U-0 U-0 U-0 U-0 U-0 U-0 R/W-0 U-0
— — — — — — POR — R = Readable bit
bit7 bit0
bit 7-2: Unimplemented: Read as '0'
bit 1: POR
bit 0: Unimplemented: Read as '0'
: Power-on Reset Status bit
1 = No Power-on Reset occurred
0 = A Power-on Reset occurred (must be set in software after a Power-on Reset occurs)
W = Writable bit
U = Unimplemented bit,
- n = Value at POR reset
read as ‘0’
DS30444E - page 28 1997 Microchip Technology Inc.
4.3 PCL and PCLATH
The program counter (PC) is 13-bits wide. The lo w byte
comes from the PCL register, which is a readable and
writable register. The upper bits (PC<12:8>) are not
readable, but are indirectly writable through the
PCLATH register. On an y reset, the upper bits of the PC
will be cleared. Figure 4-9 sho ws the two situations for
the loading of the PC. The upper example in the figure
shows how the PC is loaded on a write to PCL
(PCLATH<4:0> → PCH). The lower example in the fig-
ure shows how the PC is loaded during a CALL or GOTO
instruction (PCLATH<4:3> → PCH).
FIGURE 4-9: LOADING OF PC IN
DIFFERENT SITUATIONS
PCH PCL
12 8 7 0
PC
PCLATH<4:0>
5
PCLATH
PCH PCL
12 11 10 0
PC
2
8 7
PCLATH<4:3>
PCLATH
11
8
Instr
uction with
PCL as
Destination
ALU result
GOTO, CALL
Opcode <10:0>
PIC16C9XX
Note 1: There are no status bits to indicate stack
overflow or stack underflow conditions.
Note 2: There are no instructions/mnemonics
called PUSH or POP. These are actions
that occur from the execution of the
CALL, RETURN, RETLW, and RETFIE
instructions, or the vectoring to an interrupt address.
4.4 Program Memory Paging
PIC16C9XX devices are capable of addressing a continuous 8K word block of program memory. The CALL
and GOTO instructions provide only 11 bits of address
to allow branching within any 2K program memory
page. When doing a CALL or GOTO instruction the
upper 2 bits of the address are provided by
PCLATH<4:3>. When doing a CALL or GOTO instruction, the user must ensure that the page select bits are
programmed so that the desired program memory
page is addressed. If a return from a CALL instruction
(or interrupt) is executed, the entire 13-bit PC is pushed
onto the stack. Therefore, manipulation of the
PCLATH<4:3> bits are not required for the return
instructions (which POPs the address from the stack).
Note: The PIC16C9XX ignores paging bit
PCLATH<4>, which is used to access program memory pages 2 and 3. The use of
PCLATH<4> as a general purpose
read/write bit is not recommended since
this may affect upward compatibility with
future products.
4.3.1 COMPUTED GOTO
A computed GOT O is accomplished by adding an offset
to the program counter (ADDWF PCL). When doing a
table read using a computed GOTO method, care
should be exercised if the tab le location crosses a PCL
memory boundary (each 256 byte block). Refer to the
application note
“Implementing a Table Read”
(AN556).
4.3.2 STACK
The PIC16CXXX family has an 8 level deep x 13-bit
wide hardware stack. The stack space is not part of
either program or data space and the stack pointer is
not readable or writable. The PC is PUSHed onto the
stack when a CALL instruction is executed or an interrupt causes a branch. The stack is POPed in the event
of a RETURN, RETLW or a RETFIE instruction execution. PCLATH is not affected by a PUSH or POP operation.
The stack operates as a circular buff er . This means that
after the stack has been PUSHed eight times, the ninth
push overwrites the value that was stored from the first
push. The tenth push overwrites the second push (and
so on).
1997 Microchip Technology Inc. DS30444E - page 29
PIC16C9XX
Example 4-1 shows the calling of a subroutine in
page 1 of the program memory . This example assumes
that PCLA TH is sa ved and restored by the interrupt service routine (if interrupts are used).
EXAMPLE 4-1: CALL OF A SUBROUTINE IN
PAGE 1 FROM PAGE 0
ORG 0x500
BSF PCLATH,3 ;Select page 1 (800h-FFFh)
CALL SUB1_P1 ;Call subroutine in
: ;page 1 (800h-FFFh)
:
:
ORG 0x900
SUB1_P1: ;called subroutine
: ;page 1 (800h-FFFh)
:
RETURN ;return to Call subroutine
;in page 0 (000h-7FFh)
4.5 Indirect Addressing, INDF and FSR
Registers
The INDF register is not a physical register . Addressing
the INDF register will cause indirect addressing.
Indirect addressing is possible by using the INDF register. Any instruction using the INDF register actually
accesses the register pointed to by the File Select Register (FSR). Reading the INDF register itself indirectly
(FSR = '0') will produce 00h. Writing to the INDF register indirectly results in a no-operation (although status
bits may be affected). An effective 9-bit address is
obtained by concatenating the 8-bit FSR register and
the IRP bit (STATUS<7>), as shown in Figure 4-10.
A simple program to clear RAM locations 20h-2Fh
using indirect addressing is shown in Example 4-2.
EXAMPLE 4-2: INDIRECT ADDRESSING
movlw 0x20 ;initialize pointer
movwf FSR ;to RAM
NEXT clrf INDF ;clear INDF register
incf FSR,F ;inc pointer
btfss FSR,4 ;all done?
goto NEXT ;no clear next
CONTINUE
: ;yes continue
FIGURE 4-10: DIRECT/INDIRECT ADDRESSING
RP1:RP0 6
bank select location select
For memory map detail see Figure 4-2.
from opcode
Data
Memory
0
00 01 10 11
00h
7Fh
Bank 0 Bank 1 Bank 2 Bank 3
Indirect AddressingDirect Addressing
IRP FSR register
bank select
7
location select
00h
7Fh
0
DS30444E - page 30 1997 Microchip Technology Inc.
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