CY8C20X34 CYPRESS [Cypress Semiconductor], CY8C20X34 Datasheet - Page 45

• Manufacturer Part Number: CY8C20X34
• Description: Technical Reference Manual (TRM)
• Manufacturer: CYPRESS [Cypress Semiconductor]

4.3
Successful programming and erase operations, on the
Flash, require you to set the CLOCK and DELAY parame-
ters correctly. To determine the proper value for the DELAY
parameter only, you must consider CPU speed. Use three
factors to determine the proper value for CLOCK: operating
temperature, CPU speed, and characteristics of the individ-
ual device. Equations and additional information on calculat-
ing the DELAY and CLOCK values follow.
4.3.1
To determine the proper value for the DELAY parameter,
you must consider CPU speed during a Flash operation.
Equation 1 displays the equation for calculating DELAY
based on a CPU speed value. In this equation the units for
CPU are hertz (Hz).
Equation 2 shows the calculation of the DELAY value for a
CPU speed of 12 MHz. The numerical result of this calcula-
tion should be rounded to the nearest whole number. In the
case of a 12 MHz CPU speed, the correct value for DELAY
is 86 (0x56).
4.3.2
The CLOCK parameter must be calculated using different
equations for erase and write operations. The erase value
for CLOCK must be calculated first. In Equation 3, the erase
CLOCK value is indicated by a subscript E after the word
CLOCK. In Equation 5, the write CLOCK value is indicated
by a subscript W after the word CLOCK.
Before either CLOCK value can be calculated, the values for
M, B, and Mult must be determined. These are device spe-
cific values that are stored in the Flash Table 3 and are
accessed by way of the TableRead SROM function (see the
“TableRead Function” on page
ture is at or below 0°C, use the cold values. For operating
temperatures at or above 0°C, use the hot values. See
Table 4-11
Equations for calculating the correct value of CLOCK for
write operations are first introduced with the assumption that
the CPU speed is 12 MHz. The equation for calculating the
CLOCK value for an erase Flash operation is shown in
Equation 3. In this equation the T has units of °C.
PSoC CY8C20x34 TRM, Version 1.0
DELAY
3MHz
DELAY
for more information.
Clocking Strategy
≤
DELAY Parameter
CLOCK Parameter
CPU 12MHz
=
=
100
--------------------------------------------------------- -
100 10
---------------------------------------------------------------
≤
×
×
10
6 –
6 –
13
⋅
13
⋅
12 10
CPU 80
43). If the operating tempera-
×
–
6
–
,
80
Equation 1
Equation 2
Using the correct values for B, M, and T, in the equation
above, is required to achieve the endurance specifications
of the Flash. However, for device programmers where this
calculation is difficult to perform, the equation is simplified by
setting T to 0°C and using the hot value for B and M. This
simplification is acceptable only if the total number of erase
write cycles are kept to less than 10 and the operation is
performed near room temperature. When T is set to ‘0’,
Equation 3 simplifies to.
Once a value for the erase CLOCK value is determined, the
write CLOCK value can be calculated. The equation to cal-
culate the CLOCK value for a write is.
In this equation, the correct value for Mult must be deter-
mined, based upon temperature, in the same way that the B
and M values were determined for Equation 3.
CLOCK
CLOCK
CLOCK
W
=
E
CLOCK
----------------------------------------
=
E
B
=
–
2M T
--------------- -
64
B
256
E
Supervisory ROM (SROM)
⋅
⋅
Mult
Equation 3
Equation 4
Equation 5
45