Table of Contents
Advertisement
The following two examples calculate the PPW_VALUE for a 100-µs pulse width with an 8-MHz
and a 16-MHz crystal, respectively.
8 100
------------------ - 1
PPW_VALUE
=
16
----------------------
PPW_VALUE
=
You can use the following simplified equation to calculate the PPW_VALUE for a 100-µs pulse
width at various frequencies:
(
PPW_VALUE
=
PPW (or SP_PPW)
The PPW register is loaded from the external EPROM (locations 14H and 15H) in auto programming
mode. The SP_PPW register is loaded from the internal test ROM in serial port programming mode.
The default pulse width for serial port programming is longer than required, so you should change the
value before beginning to program the device. (See "Changing Serial Port Programming Defaults" on
page 16-34.) The PPW_VALUE determines the programming pulse width, which must be at least 100
µs for successful programming.
15
1
PPW14
7
PPW7
PPW6
Bit
Bit
Number
Mnemonic
15
1
14:0
PPW14:0
Figure 16-2. Programming Pulse Width Register (PPW or SP_PPW)
×
800
--------- - 1
4.5552 5
–
=
–
=
144
144
×
100
1600
------------ - 1
1
–
=
–
=
144
144
×
)
0.6944
F
–
1
osc
PPW13
PPW12
PPW5
PPW4
Set this bit for proper device operation.
PPW_VALUE.
This value establishes the programming pulse width for auto programming
or serial port programming. For a 100-µs pulse width, use the following
formula and round the result to the next higher integer. For auto
programming, write this value to the external EPROM (see "Auto
Programming Procedure" on page 16-30). For serial port programming,
write this value to the internal memory (see "Changing Serial Port
Programming Defaults" on page 16-34).
(
PPW_VALUE
0.6944 F
=
PROGRAMMING THE NONVOLATILE MEMORY
≈
05 H
=
≈
10.11
11
0BH
=
PPW11
PPW10
PPW3
PPW2
Function
×
)
1
–
os c
no direct access
8
PPW9
PPW8
0
PPW1
PPW0
16-9
Advertisement
Table of Contents
