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From: rnelson@wsuaix.csc.wsu.edu (roger nelson)
Subject: 8bit microcontroller compendium
Message-ID: <CrqBEC.CIp@serval.net.wsu.edu>
Sender: news@serval.net.wsu.edu (Greg Bell)
Organization: Washington State University
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Date: Tue, 21 Jun 1994 04:06:12 GMT
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                8 Bit microcontroller compendium 

This table consist of two parts: memory and pin counts, and 
features and peripherals.

Manufacturer microcontroller descriptions often fail to summarize
the microcontroller features in a way that allows one to quickly identify
features across the full line.  (Motorola used to have some neat 
pie/sector charts in the brown books (1987?)). 

This tabular crossreference is intended to serve as a quick lookup for a
microcontroller that might have desired features for a particular application.

For the Motorola line, refer to my mc68xx pinout guides to see a more
detailed breakdown of the pin functions and port capabilities (the 
6800, 6801, 6802, 6803, 6804, 6805, and 6811 families are cross referenced).

Keep in mind that most of these microcontrollers operate in several modes.
For example, in single chip mode, external memory expansion may not be 
available, or general purpose I/O lines may be replaced with memory address
ports.

Send additions, corrections, suggestions or comments to:

   Roger Nelson   rnelson@wsuaix.csc.wsu.edu

Blank entries are missing data the needs to be filled in.
- entries indicate the processor does support this feature.

Motorola
                                             Boot Exp TotalG.P.G.P.
                               OTP  EP   EEP strp Mem I/O  In  Out I/O
           Tech Pins  RAM ROM  ROM  ROM  ROM mode (k) pins linelineline
6800       HMOS    40  -   -   -    -    -   -    64
6801       HMOS    40 128 2048 -    -    -        64    29
6803       HMOS    40 128 -    -    -    -        64    13
6801u4     HMOS    40 192 4096 -    -    -        64    29
6803u4     HMOS    40 192 -    -    -    -        64    13
68701      HMOS    40 128 -    -    2048 -        64    29
68701u4    HMOS    40 192 -    -    4096 -        64    29
6802       HMOS                          -        64
6804j1     HMOS    20  30  512 -    -    -        64    12
6804j2     HMOS    20  30 1000 -    -    -        64    12
6804p2     HMOS    28  30 1016 -    -    -        64    20
68704p2    HMOS    28  30 -    -    1020 -        64    20
68hc04j2   HCMOS   20 172 1000 -    -    -        64    12
68hc04j3   HCMOS   20  30 1672 -    -    -        64    12
68hc04p4   HCMOS   28 172 3700 -    -    -        64    20
68hc704p4  HCMOS   28 172 -    -    3700 -        64    20
6805p2     HMOS    28  64 1110 -    -    -        64    20
6805p6     HMOS    28  64 1804 -    -    -        64    20
6805r3     HMOS 40/44 112 3776 -    -    -        64    32
6805s2     HMOS    28  64 1480 -    -    -        64    21
6805u2     HMOS 40/44  64 2048 -    -    -        64    32
6805u3     HMOS 40/44 112 3376 -    -    -        64    32
68075p3    HMOS    28 112 -    -    1804 -        64    20
68705p5    HMOS    28 112 -    -    1804 -        64    20
68705r3    HMOS    40 112 -    -    3776 -        64    32
68705r5    HMOS    40 112 -    -    3776 -        64    32
68705s3    HMOS    28 104 -    -    3752 -        64    21
68705u3    HMOS    40 112 -    -    3776 -        64    32
68705u5    HMOS    40 112 -    -    3776 -        64    32
68hc05a6   HCMOS40/44 176 4160 -    -    2056     64    32
68hc05b4   HCMOS48/52 176 4160 -    -    -        64    32
68hc05b6   HCMOS40/52 176 5952 -    -     256     64    32
68hc05c2   HCMOS   40 176 2096 -    -    -        64    32
68hc05c3   HCMOS   40 176 2096 -    -    -        64    32
68hc05c4   HCMOS40/44 176 4160 -    -    -        64    32
68hc05c8   HCMOS40/44 176 7700 -    -    -        64    32
68hc05c9   HCMOS      176      -    -    -        64    32
68hc05l6   HCMOS   68 176 6208 -    -    -        64    32
68hc05m4   HCMOS   52 128 4096 -    -    -        64    32
68hc05p1   HCMOS               -    -    -        64    32
68hcl05c4  HCMOS40/44 176 4160 -    -    -        64    32
68hcl05c8  HCMOS40/44 176 8192 -    -    -        64    32
68hsc05c4  HCMOS40/44 176 4160 -    -    -        64    32
68hsc05c8  HCMOS40/44 176 8192 -    -    -        64    32
68hc705b5  HCMOS48/52 176 -    -    -    -        64    32
68hc705c4  HCMOS40/44 176      -    -    -        64    32
68hc705c8  HCMOS40/44 304 -    -    -    -        64    32
68hc805b6  HCMOS48/52 176 -    -    8k   6208     64    32
68hc805c4  HCMOS40/44 176 -    -    -    4160     64    32
146805e2   CMOS    40 112    0 -    -    -        64    16
146805f2   CMOS    28  64 1089 -    -    -        64    20
146805g2   CMOS    40 112 2106 -    -    -        64    32
6809       HMOS                                   64
6809e      HMOS                                   64
6810       HMOS                                   64
68hc11a0   HCMOS48/52 256 -    -    -    -        64    38
68hc11a1   HCMOS48/52 256 -    -    -     512  y  64    38
68hc11a8   HCMOS48/52 256 8192 -    -     512  y  64    38
68hc11d3   HCMOS40/44 192 4096 -    -    -     y  64    30
68hc11e1   HCMOS   52 512    0 -    -     512  y  64    38
68hc11e9   HCMOS   52 512 12k  -    -     512  y  64    38
68hc11f1   HCMOS          -    -    -    -     y  64  -
68hc11d3   HCMOS      192      -    -    -     y  64    38
68hc11e2   HCMOS48/52 256 -    -    -    2048  y  64    38

68hc705c8  HCMOS40/44 304 -    7616 -    -        64    24
68hc711d3  HCMOS40/44 192 -    4096 -    -        64    24
68hc711a8  HCMOS   52 256 -    8192 -    -        64    38
68hc711e9  HCMOS48/52 512 -    12k  -    -        64    38


Although the expanded multiplex mode of the 68HC11 RAM memory expansion to
64k uses 16 output pins for addressing (2 8 bit ports), the MC68HC24
peripheral chip allows the processor to address 64k external memory while
preserving the two I/O ports.

Intel MCS family
                                                  Exp TotalG.P.G.P.
                               OTP  EP   EEP Boot Mem I/O  In  Out I/O
           Tech Pins  RAM ROM  ROM  ROM  ROM  ROM (k) pins linelineline
8051       HMOS       128  4k  -    -    -        64
8031       HMOS       128 -    -    -    -        64

8051AH     HMOS       128  4k  -    -    -        64
8031AH     HMOS       128 -    -    -    -        64
8751H      HMOS       128  4k  -    y?   -        64
8751BH     HMOS       128  4k  -    y?   -        64

8052AH     HMOS       256  8k  -    -    -        64
8032AH     HMOS       256 -    -    -    -        64
8752BH     HMOS       256  8k  -    y?   -        64
80C51BH    HMOS       128  4k  -    -    -        64
80C31BH    HMOS       128 -    -    -    -        64
87C51      HMOS       128  4k  -    y?   -        64

83C51FA    HMOS       256  8k  -    -    -        64
80C51FA    HMOS       256 -    -    -    -        64
87C51FA    HMOS       256  8k  -    y?   -        64

83C51FB    HMOS       256 16k  -    -    -        64
80C51FA    HMOS       256 -    -    -    -        64
87C51FB    HMOS       256 16k  -    y?   -        64

83C51GA    HMOS       128  4k  -    -    -        64
80C51GA    HMOS       128 -    -    -    -        64
87C51GA    HMOS       128  4k  -    y?   -        64

83C152JA   HMOS       256  8k  -    -    -        64
80C152JA   HMOS       256 -    -    -    -        64


80C152JB   HMOS       256 -    -    -    -        64

83C152JC   HMOS       256  8k  -    -    -        64
80C152JC   HMOS       256 -    -    -    -        64

80C152JD   HMOS       256 -         -    -        64

83C451     HMOS       128  4k  -    -    -        64
80C451     HMOS       128 -    -    -    -        64

83C452     HMOS       256  8k  -    -    -        64
80C452     HMOS       256 -    -    -    -        64
87C452P    HMOS       256  8k  -    y?   -        64

Texas Instruments TMS370
                                                  Exp TotalG.P.G.P.
                               OTP  EP   EEP Boot Mem I/O  In  Out I/O
           Tech Pins  RAM ROM  ROM  ROM  ROM  ROM (k) pins linelineline
370C010      ?     28 128  4k   -     -   -    ?   -    22   1   0  21
370C050      ?     68 256  4k   -     -   -    ?  112   55   9   0  46
370C032      ?     44 256  8k   -     -   -    ?   -    36  13   9  14
370C052      ?     68 256  8k   -     -   -    ?  112   55   9   0  46
370C056      ?     68 512 16k   -     -   -    ?  112   55   9   0  46

370C310      ?     28 128  4k   -     -   -    ?   -    22   1   0  21
370C350      ?     68 256  4k   -     -   -    ?  112   55   9   0  46
370C332      ?     44 256  8k   -     -   -    ?   -    36  13   9  14
370C352      ?     68 256  8k   -     -   -    ?  112   55   9   0  46
370C356      ?     68 512 16k   -     -   -    ?  112   55   9   0  46

370C150      ?     68 256   -   -     -   -    ?  112   55   9   0  46
370C250      ?     68 256   -   -     -   -    ?  112   55   9   0  46
370C156      ?     68 512   -   -     -   -    ?  112   55   9   0  46
370C256      ?     68 512   -   -     -   -    ?  112   55   9   0  46

370C810      ?     28 128   -   -     -  4k    ?   -    22   1   0  21
370C850      ?     68 256   -   -     -  4k    ?  112   55   9   0  46
370C732      ?     44 256   -   -    8k   -    ?   -    36  13   9  14
370C756      ?     68 512   -   -   16k   -    ?  112   55   9   0  46

The Texas Instruments TMS370 series have either a 256 byte EEPROM
(the 370Cx56 models have a 512 byte EEPROM) for data memory with the
exception of the TMS3703xx which have none.


National Semiconductor COP800
                                                  Exp TotalG.P.G.P.
                               OTP  EP   EEP Boot Mem I/O  In  Out I/O
           Tech Pins  RAM ROM  ROM  ROM  ROM  ROM (k) pins linelineline
800C       MCMOS

820C       MCMOS 28    64  1k   -    -     -       32  24
821C       MCMOS 24    64  1k   -    -     -           20
822C       MCMOS 20    64  1k   -    -     -           16
840C       MCMOS 28   128  2k   -    -     -       32  24
841C       MCMOS 24   128  2k   -    -     -           20
842C       MCMOS 20   128  2k   -    -     -           16
620C       MCMOS 28    64  1k   -    -     -           24
621C       MCMOS 24    64  1k   -    -     -           20
622C       MCMOS 20    64  1k   -    -     -           16
640C       MCMOS 28   128  2k   -    -     -           24
641C       MCMOS 24   128  2k   -    -     -           20
642C       MCMOS 20   128  2k   -    -     -           16

820CB      MCMOS
821CB      MCMOS
822CB      MCMOS

8640C      MCMOS 28    64  2k   -    -    64           24
8641C      MCMOS 24    64  2k   -    -    64           20
8642C      MCMOS 20    64  2k   -    -    64           16
8620C      MCMOS 28    64  1k   -    -    64           24
8621C      MCMOS 24    64  1k   -    -    64           20
8622C      MCMOS 20    64  1k   -    -    64           16

8720C      MCMOS 28    64  1k   -    -    64           24
8721C      MCMOS 24    64  1k   -    -    64           20
8722C      MCMOS 20    64  1k   -    -    64           16

880        MCMOS
888CF      MCMOS40/44 128  4k   -    -     -      32  33/37
888CG      MCMOS40/44 192  4k   -    -     -          35/3 9
888CL      MCMOS40/44 128  4k   -    -     -      32  33/39
820CP-X    MCMOS
840CP-X    MCMOS

888CLP     MCMOS28/40 128  -
884CLP     MCMOS28/40 128  -

888CFP     MCMOS28/40 128  -                          21/33
884CFP     MCMOS28/40 128  -                          21/33

888CGP     MCMOS28/40 192  -                          23/35
884CGP     MCMOS28/40 192  -                          23/35

888CLMH    MCMOS  44  128  -             8k             37
888CFMH    MCMOS  44  128  -             8k             37
888CGMH    MCMOS  44  192  -             8k             39

The ports D and L are used to address external memory in ROMless mode.

__________________________________________________________________________

A/D converters are provided on several microcontroller models.
In some models an interrupt is generated when the conversion is complete
in others, the program must wait for a conversion to complete (MC68xx).
Some microcontrollers may not have A/D converters, but may have simpler
differential comparators (com).

Interrupt sources/vectors.  Some of the sources may be dedicated to
processor functions such as: software traps, timer functions,
serial device, wake up or watch dog functions.

Memory mapped I/O.  All the processor listed here use memory mapped I/O.

The watch dog timer can be used to catch programs that get stuck in
infinate loops.  The w.d.t may reset the processor and external system.

Computer operating properly will reset the system if the clock rate
falls below operating limits.

The 8/16/32 bit timers may have modes which allow them to clock events
internally or externally, refer to the chip's data book.
Some controllers such as the MC6811 series have a special pulse accumulator
which allows a counter to be incremented on rising or falling (selectable)
edges without have to interrupt the program.  The program can pull the
counter register for the current value, the N.S. COP family allows the timer
to be programmed for this functionality.

Syncronous serial ports are often used to communicate with other
peripherals using syncronous serial protocols such as memory servers,
display drivers, additional A/D ports, etc., or a simple network of
micro controllers in a master/slave configuration.
This allows communication with these devices using just a few pins
without taking 2 or 3 data/address ports for memory mapped I/O.

The SPI is a syncronous serial port (serial peripheral interface)
The SPI doesn't require start/stop bits and can operate at higher
clock rates.

The MicroWire/Plus in the National Semiconductor family is a
syncronous serial port similar to an SPI.

Asyncronous serial ports are often configured to be used as an RS-232 port.

The SCI is a asyncronous serial port (serial communication interface)
This port can be configured for communication with an RS-232 port
by providing the necessary voltage augmentation such as a MAX233 chip.

The UART is an asyncronous serial port similar to the SCI, but it is
double buffered (2 bytes) allowing for faster operation with less
chance for overrun errors.

SCI and UART functions may feature an (attention or wake up mode) which
monitors the input for an address character (flagged by bit 9 set).
An interrupt is generated where the program may determine based on the
address value to receive the following input data.

Keep in mind that the SCI and UART are not identical devices; also,
SCI capabilities may vary within a family line.


Motorola
               Int Mem Wch Min  Bus                   8  16  32
           A/D src map dog clk  spd         NMI Msk bit bit bit Pls
           Chn vct I/O tmr rate Mhz SPC SCI Int Int tim tim tim acc.
6800         -      y
6801         -      y                -   y           -   1   -
6803         -      y                -   y           -   1   -
6801u4       -      y                -   y           -   1   -
6803u4       -      y                -   y           -   1   -
68701        -      y                -   y           -   1   -
68701u4      -      y                -   y           -   1   -
6802         -      y                                -   -   -
6804j1       -      y                                1   -   -
6804j2       -      y                                1   -   -
6804p2       -      y                                1   -   -
68704p2      -      y                                1   -   -
68hc04j2     -      y                                1   -   -
68hc04j3     -      y                                1   -   -
68hc04p4     -      y                                1   -   -
68hc704p4    -      y                                1   -   -
6805p2       -      y                -               1   -   -   4
6805p6       -      y                -               1   -   -   4
6805r3       4      y                -               1   -   -   4
6805s2       4      y                y               1   -   -   4
6805u2       4      y                y               1   -   -   4
6805u3       -      y                -               1   -   -   4
68075p3      -      y                -               1   -   -   4
68705p5      -      y                -               1   -   -
68705r3      -      y                -               1   -   -
68705r5      4      y                -               1   -   -
68705s3      4      y                -               1   -   -
68705u3      4      y                y               2   1   -
68705u5      -      y                -               1   -   -
68hc05a6     -      y                -               1   -   -   4
68hc05b4     -      y                y  y                1   -   4
68hc05b6     4      y                -  y                1   -   4
68hc05c2     4      y                -  y                1   -   4
68hc05c3     -      y                -  -                1   -   4
68hc05c4     -      y                y  y                1   -   4
68hc05c8     -      y                y  y                1   -   4
68hc05c9     -      y                y  y                1   -   4
68hc05l6     -      y                y  y                1   -   4
68hc05m4     -      y                y  -                1   -   4
68hc05p1     6      y                -  -            1   1   -   4
68hcl05c4    -      y                y  y                1   -   4
68hcl05c8    -      y                y  y                1   -   4
68hsc05c4    -      y                y  y                1   -   4
68hsc05c8    -      y                y  y                1   -   4
68hc705b5    -      y                y  y                1   -
68hc705c4    -      y                y  y                1   -
68hc705c8    -      y                y  y                1   -
68hc805b6    -      y                y  y                1   -
68hc805c4    -      y                -  y                1   -
146805e2     -      y                y  y                1   -
146805f2     -      y                -  -            1       -
146805g2     -      y                -  -            1       -
6809         -      y                -  -            1       -
6809e        -      y                                        -
6810         -      y                                        -
68hc11a0     8      y                y  y                        1
68hc11a1     8      y                y  y                        1
68hc11a8     8      y                y  y                        1
68hc11d3     -      y                -  y                        1
68hc11e1     8      y                y  y                        1
68hc11e9     8      y                y  y                        1
68hc11f1     8      y                -  -                        1
68hc11d3     -      y                y  y                        1
68hc11e2     8      y                y  y                        1

68hc705c8    -      y                y  y
68hc711d3    -      y                y  y
68hc711a8    y      y                y  y
68hc711e9    y      y                y  y
68hc811e2    8      y                y  y

Since no interrupt is generated at the completion of an A/D conversion,
the data registers must be polled.

The 680x series SCI has fixed baud rate, the 6811 series offers the
addition of software selectable baud rates and interrupt drive operation.



Intel MCS family
                Int Mem Wch Min  Bus S G             Timer/pulse
           A/D  src map dog clk  spd E S     NMI Msk accumulator Pls
           Chn  vct I/O tmr rate Mhz P P UARTInt Int   9  16  32 acc.
8051         -  6/5  y   y           - -   y        -   2   -
8031         -  6/5  y   y           - -   y        -   2   -

8051AH       -  6/5  y   y           - -   y        -   2   -
8031AH       -  6/5  y   y           - -   y        -   2   -
8751H        -  6/5  y   y           - -   y        -   2   -
8751BH       -  6/5  y   y           - -   n?       -   2   -

8052AH       -  8/6  y   y           - -   y        -   3   -
8032AH       -  8/6  y   y           - -   y        -   3   -
8752BH       -  8/6  y   y           - -   y        -   3   -
80C51BH      -  6/5  y   y           - -   y        -   2   -
80C31BH      -  6/5  y   y           - -   y        -   2   -
87C51        -  6/5  y   y           - -   y        -   2   -

83C51FA      - 14/7  y   y           - -   y        -   3   -
80C51FA      - 14/7  y   y           - -   y        -   3   -
87C51FA      - 14/7  y   y           - -   y        -   3   -

83C51FB      - 14/7  y   y           - -   y        -   3   -
80C51FA      - 14/7  y   y           - -   y        -   3   -
87C51FB      - 14/7  y   y           -     y        -   3   -

83C51GA      8  8/7  y   y           y -   y        -   2   -
80C51GA      8  8/7  y   y           y -   y        -   2   -
87C51GA      8  8/7  y   y           y -   y        -   2   -

83C152JA     - 19/11 y   y           - y   y        -   2   -
80C152JA     - 19/11 y   y           - y   y        -   2   -


80C152JB     - 19/11 y   y           - y   y        -   2   -

83C152JC     - 19/11 y   y           - y   y        -   2   -
80C152JC     - 19/11 y   y           - y   y        -   2   -

80C152JD     - 19/11 y   y           - y   y        -   2   -

83C451       -  6/5  y   y           - -   y        -   2   -
80C451       -  6/5  y   y           - -   y        -   2   -

83C452       -  9/8  y   y           - -   y        -   2   -
80C452       -  9/8  y   y           - -   y        -   2   -
87C452P      -  9/8  y   y           - -   y        -   2   -

* Depending on the selected mode, Each timer may be either one 8bit,
  or one 16bit or 2 8bit timers.

The UART is double buffered

The A/D conversion generates an interrupt

Texas Instruments TMS370 series
                Int Mem Wch Min  Bus                   8  16  32
           A/D  src map dog clk  spd         NMI Msk bit bit bit Pls
           Chn  vct I/O tmr rate Mhz SPC SCI Int Int tim tim tim acc.

370C010      -  6/13 y   y  2-20      y   -   ?   ?   ?   ?   ?
370C050      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?
370C032      8 23/25 y  pact2-20     pact y   ?   ?   ?   ?   ?
370C052      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?
370C056      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?

370C310      -  6/13 y   y  2-20      y   -   ?   ?   ?   ?   ?
370C350      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?
370C332      8 23/25 y      2-20     pact y   ?   ?   ?   ?   ?
370C352      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?
370C356      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?

370C150      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?
370C250      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?
370C156      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?
370C256      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?

370C810      -  6/13 y   y  2-20      y   -   ?   ?   ?   ?   ?
370C850      8 10/23 y  pact2-20      y   y   ?   ?   ?   ?   ?
370C732      8 23/25 y   y  2-20     pact y   ?   ?   ?   ?   ?
370C756      8 10/23 y   y  2-20      y   y   ?   ?   ?   ?   ?

The TI A/D system only has one data register, thus only one conversion can
be done at a time.

I'm not sure if the pact is built in to the microcontroller or is offered
as peripheral component.


National Semiconductor

               Int Mem Wch Min  Bus Micro             8  16  32
           A/D src map dog clk  spd wire    NMI Msk bit bit bit Pls
           Chn vct I/O tmr rate Mhz ser UARTInt Int tim tim tim acc.

800C                y                 y               -  1   -

820C        -  3    y                 y               -  1   -
821C        -  3    y                 y               -  1   -
822C        -  3    y                 y               -  1   -
840C        -  3    y                 y               -  1   -
841C        -  3    y                 y               -  1   -
842C        -  3    y                 y               -  1   -
620C        -  3    y                 y               -  1   -
621C        -  3    y                 y               -  1   -
622C        -  3    y                 y               -  1   -
640C        -  3    y                 y               -  1   -
641C        -  3    y                 y               -  1   -
642C        -  3        y                 y               -  1   -

820CB               y                 y
821CB               y                 y
822CB               y                 y

8640C       -  3    y                 y              -   1   -
8641C       -  3    y                 y              -   1   -
8642C       -  3    y                 y              -   1   -
8620C       -  3    y                 y              -   1   -
8621C       -  3    y                 y              -   1   -
8622C       -  3    y                 y              -   1   -

8720C       -  3    y                 y              -   1   -
8721C       -  3    y                 y              -   1   -
8722C       -  3    y                 y              -   1   -

880         -  ?    y   -             y              -   1   -
888CL       - 10    y   y             y              -   1   -
888CF       8 10    y                 y              -   2   -
888CG       - 14    y                 y  y           -   3   -
820CP-X             y                 y
840CP-X             y                 y

888CLP        10    y   y             y              -   2   -
884CLP        10    y   y             y              -   2   -

888CFP      8 10    y   y             y              -   2   -
884CFP      8 10    y   y             y              -   2   -

888CGP    2com14    y   y             yp y           -   3   -
884CGP    2com14    y   y             yp y           -   3   -

888CLMH     - 10    y   y             y  -           -   2   -
888CFMH     8 10    y   y             y  y           -   2   -
888CGMH   2com14    y   y             yp y           -   3   -

The N.S. timers have three modes of operation:
1 - Processor independent mode: once operation parameter have been setup
    output signals are generated automatically without additional program
    intervation when the timer counts down to 0 (underflow).
2 - External event counter mode: The timer counts pulse event on an
    input pin and generates and interrupt when the timer counts down to 0.
3 - Input Capture mode: The timer counts at a fixed rate, when a pulse
    event occurs on an input pin, the current counter value is copied to
    a timer register and an interrupt is generated.


References:

Motorolla Microprocessor, Microcontroller and Peripheral Databook
vols. I and II  (1988)

National Semiconductor Microcontroller Databook (1989)

Hitz, Kenneth  and Tabak, Daniel
Microcontrollers: Architecture, Implementation , & Programming
McGraw-Hill Inc.  1992



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