ez80f92 ZiLOG Semiconductor, ez80f92 Datasheet - Page 208

• Manufacturer Part Number: ez80f92
• Description: Ez80acclaim Flash Microcontrollers
• Manufacturer: ZiLOG Semiconductor

PS015313-0508
Flash Frequency Divider Register
The 8-bit frequency divider allows programming to Flash over a range of system clock
frequencies. Flash can programmed with system clock frequencies ranging from 154 kHz
through 50 MHz. The Flash controller requires an input clock with a period that falls
within the range of 5.1 µs to 6.5 µs. The period of the Flash controller clock is set through
the Flash Frequency Divider register. Writes to this register are allowed only after it is
unlocked via the FLASH_KEY register. The Frequency Divider register value required
versus system clock frequency is listed in
the ranges shown in this table are not supported.
Table 117. Flash Frequency Divider Values
Table 118. Flash Frequency Divider Register; (FLASH_FDIV = 00F9h)
System Clock Frequency
154–196 kHz
308–392 kHz
462–588 kHz
616 kHz–50 MHz
Note: *The CEILING function rounds fractional values up to the next whole
Bit
Reset
CPU Access
Note: R/W = Read/Write, R = Read Only. *Key sequence required to enable Writes
Bit
Position
[7:0]
FLASH_FDIV
number, for example, CEILING(3.01) is 4.
Value Description
01h–
FFh
R/W*
Divider value for generating the required 5.1–6.5 μs Flash
controller clock period.
7
0
R/W*
Flash Frequency Divider Value
CEILING [System Clock Frequency
1
2
3
(MHz) x 5.1 (μs)]*
6
0
Table
R/W*
5
0
117. System clock frequencies outside of
R/W*
4
0
R/W*
3
0
Product Specification
R/W*
2
0
eZ80F92/eZ80F93
R/W*
1
0
Flash Memory
R/W
0
1
201