Z8F640x/Z8F480x/Z8F320x/Z8F240x/Z8F160x
Z8 Encore!®
147
Flash Frequency High and Low Byte Registers
The Flash Frequency High and Low Byte registers combine to form a 16-bit value,
FFREQ, to control timing for Flash program and erase operations. The 16-bit binary Flash
Frequency value must contain the system clock frequency (in kHz) and is calculated using
the following equation:.
System Clock Frequency
---------------------------------------------------------------
FFREQ[15:0] = {FFREQH[7:0],FFREQL[7:0]} =
1000
Caution:
Flash programming and erasure is not supported for system clock frequen-
cies below 32KHz (32768Hz) or above 20MHz. The Flash Frequency
High and Low Byte registers must be loaded with the correct value to in-
sure proper operation of the Z8F640x family device.
Table 88. Flash Frequency High Byte Register (FFREQH)
BITS
FIELD
RESET
R/W
7
6
5
4
3
2
1
0
FFREQH
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
FFAH
ADDR
FFREQH—Flash Frequency High Byte
High byte of the 16-bit Flash Frequency value.
Table 89. Flash Frequency Low Byte Register (FFREQL)
BITS
FIELD
RESET
R/W
7
6
5
4
3
2
1
0
FFREQL
0
0
0
0
0
0
0
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
FFBH
ADDR
FFREQL—Flash Frequency Low Byte
Low byte of the 16-bit Flash Frequency value.
PS017610-0404
Flash Memory
ZILOG [ ZILOG, INC. ]
