SPMC68CK338CPV14 datasheet(87/133 Pages) FREESCALE

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MC68CK338

MOTOROLA

MC68CK338TS/D

CPTR — CPSM Test Register

$YFF40A

CPTR is used during factory testing of the CTM6. Accesses to CPTR must be made while the MCU is

in test mode.

6.6 Clock Sources for Counter Submodules

One of seven clock sources can be chosen for each counter submodule. Five of them are fixed

prescaler taps derived from the system clock:

÷2, ÷4, ÷8, ÷16, and ÷32. A sixth prescaler tap is software

selectable as the system clock divided by 64, 128, 256, or 512. An alternate prescaler option provides

fixed prescaler taps of the system clock divided by 3, 6, 12, 24, and 48. In this case, the software se-

lectable tap is the system clock divided by 96, 192, 384, or 768.

The seventh selectable clock source is an external pin which may trigger on the rising or falling edge of

the input signal. The external input allows a clock frequency to be selected that is not based on the MCU

system clock. Alternately, the external clock input allows a counter submodule to be used for pulse or

event counting.

NOTE

The external clock inputs for MCSM30 and MCSM31 are tied to the I/O pin CTD5

for DASM5. The external clock inputs for MCSM2 and FCSM3 are tied to the I/O

pin CTD27 for DASM27.

6.7 Free-Running Counter Submodule (FCSM)

The free-running counter submodule (FCSM) has a 16-bit up counter with an associated clock source

selector, selectable time-base bus drivers, software writable control registers, software readable status

bits, and interrupt logic. When the 16-bit up counter overflows from $FFFF to $0000, an optional over-

flow interrupt may be generated.

Software selects which, if any, time-base bus is to be driven by the 16-bit counter. A software control

pin. The polarity of the external input pin is also programmable.

One FCSM is contained in the CTM6. Figure 20 shows a block diagram of the FCSM.

Table 49 Prescaler Division Ratio Select Field

Prescaler Control Register Bits

Prescaler Division Ratio

PRUN

DIV23

PSEL1 PSEL0 PCLK1 PCLK2 PCLK3 PCLK4 PCLK5 PCLK6

000000

1000248

1001248

128

1010248

256

1011248

512

110036

110136

192

111036

384

111136

768

Freescale Semiconductor, Inc.

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SPMC68CK338CPV14 Datasheet(PDF) 87 Page - Freescale Semiconductor, Inc

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