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FOUT SOURCE
Master Mode bits MM4 through MM7 specify the source input for the FOUT
Di vi der.
Fi fteen inputs are ava i 1ab1e for select i on and they inc 1ude
the five
Source pins, the five Gate pins and the five
internal
frequencies derived from the oscillator.
The 16th combination of the
four control
bits
(all
zeros)
is used to assure that an active
frequency is available on FOUT following a reset.
FOUT DIVIDER
Bits MMB through MM11 specify the dividing ratio for the FOUT Divider.
The FOUT source selected by bi ts
~1M4
through MM7 i s di vi ded by an
integer value between 1 and 16, inclusive, and is then passed to the
FOUT output buffer.
The undivided oscillator frequency is available at
FOUT simply by selecting the F1 source and a dividing ratio of one.
After power-on dr reset, the FOUT Divider is set to divide by sixteen.
FOUT GATE
~1aster
Mode bi t
~1M12
provi des a software gati ng capabi 1i ty for the FOUT
signa1.
When
M~112
=
1, FOUT is off and ina 1ow impedance state to
ground.
MM12 can be set or cleared in conjunction with the loading of
the other bits in the Master Mode register; alternatively, there are
commands that allow MM12 to be individually set or cleared directly
without changing any other Master Mode bits.
After power-up or reset,
FOUT is gated on.
BUS WIDTH
Bit MM13 controls the multiplexer at the data bus interface in order to
configure the part for an B··bit or 16-bit external bus.
Only the
16-bit configuration is used on the Am96/4116.
The internal bus is
always
16-bits
wide.
When MM13
=
0,
16-bit
internal
data
is
transferred a byte at a time to and from the eight low-order external
data bus lines.
DA T A POINTER SEQUENCE
Bi t MM14 contro'1 s the Data Poi nter 1ogi c to enable or di sab1e the
automatic sequencing functions.
When MM14
=
1, the contents of the
Data Pointer can be changed only directly by entering a command.
When
MM14
=
0, several types of automatic Data Pointer sequencing are
available.
Thus
the
host
processor,
by
controlling
MM14,
can
repetitively read/write a single internal location, or can sequentially
read/write groups of locations.
3-22
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