Z8F6421PM020SC Datasheet, PDF (209/299 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers Z8 Encore-R 64K Series

Z8 Encore!^® 64K Series
Product Specification
189
Flash Frequency High and Low Byte Registers
The Flash Frequency High and Low Byte registers (Tables 95 and 96) combine to form a
16-bit value, FFREQ, to control timing for Flash program and erase operations. The 16-bit
Flash Frequency registers must be written with the system clock frequency in KHz for
Program and Erase operations. Calculate the Flash Frequency value using the following
equation:
FFREQ[15:0] = {FFREQH[7:0],FFREQL[7:0]} = ^{S----y---s--t--e---m------C-----l-o---c---k-----F----r--e---q---u----e--n----c--y--}
1000
Caution:
Flash programming and erasure is not supported for system clock frequen-
cies below 20KHz, above 20MHz, or outside of the valid operating fre-
quency range for the device. The Flash Frequency High and Low Byte
registers must be loaded with the correct value to insure proper program
and erase times.
Table 95. Flash Frequency High Byte Register (FFREQH)
BITS
7
6
5
4
3
2
1
0
FIELD
FFREQH
RESET
R/W
ADDR
0
R/W
FFAH
Table 96. Flash Frequency Low Byte Register (FFREQL)
BITS
7
6
5
4
3
2
1
0
FIELD
FFREQL
RESET
0
R/W
R/W
ADDR
FFBH
FFREQH and FFREQL—Flash Frequency High and Low Bytes
These 2 bytes, {FFREQH[7:0], FFREQL[7:0]}, contain the 16-bit Flash Frequency value.
PS019915-1005
Flash Memory