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FOUT DIVIDER COUNTER
The 4-bit FOUT Divider is used to subdivide the source selected for the
Frequency Out pi n.
It pro vi des for di vi s i on by an integer from 1 to
16, inclusive.
The dividing ratio is selected by a 4-bit
fiel~
in the
Master Mode register.
The FOUT Divider is intended to allow a
relatively low FOUT frequency for use as a system clock while still
permitting higher resolution internal frequencies from the crystal
oscillator.
With a crystal frequency of 8MHz, for example, a divider
ratio of four with F1 selected would provide an FOUT rate of 2MHz.
In
applications that do not use FOUT as a frequency source or as a clock,
the Di vi der forms a simple genera l-purpose programmable 4-bi t di vi der
that can use any of the general input pins.
DA T A POINTER COUNTER
The 6-bit Data Pointer is used to control internal addressing for data
bus transfers via the data
port.
The Data Pointer is directly loaded
by
command
and
can
be automatically
incremented
following
data
transfers.
Figure 3-16 shows the pointer configuration.
The Byte Pointer bit is only active when the data bus is operating with
its 8-bit width option.
Whenever the Data Pointer is loaded, the Byte
Pointer bit cleared to zero.
The Byte Pointer toggles following each
8-bit data transfer with an 8-bit data bus (MM13
=
0),
or it always
remains reset with the 16-bit data bus option (MM13
=
1).
{
00
=
Alarm Register 1
I
01
=
Alarm Register 2
Control Cycle
- - - - -
10
=
Master Mode Register
Increment
11
=
Status Register/No Increment
000
=
Illegal
001
=
Counter Group 1
1
010
=
Counter Group 2
011
=
Counter Group 3
100
=
Counter Group 4
101
=
Counter Group 5
110
=
Illegal
111
=
Control Group'
IG4IG2IGl~E
- I
l L
---
Byte Pointer
1
=
Least significant Byte Transferred next
o
=
Most significant Byte Transferred next
Group Pointer
- - - - - Element Pointer
(
00
=
Mode Register
I
01
=
Load Register
Element Cycle
_ _ _ _ _
10
=
Hold Register
Increment
11
=
Hold Register/Hold Cycle Increment
- - - - - - _
..
_-----_._-----------------------_~
Figure 3-16.
Data Pointer Counter
3-24
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