EZ80F91MCU Datasheet, PDF (128/396 Pages) Zilog, Inc. – eZ80Acclaim-TM Flash Microcontrollers

eZ80F91 MCU
Product Specification
109
ler aborts the row programming operation, and software must assure that no fur-
ther Writes are performed to the row without it first being erased. It is suggested
that row programming only be used one time per row and not in combination with
single-byte Writes to the same row without first erasing it. Otherwise, the burden
is on software to ensure that the 31 ms maximum cumulative programming time
between erases is not exceeded for a row.
Memory Write
A single-byte memory Write operation uses the address bus and data bus of the
eZ80F91 device for programming a single data byte to Flash memory. While the
CPU executes a Load instruction, the Flash controller asserts the internal WAIT
signal to stall the CPU until the Write is complete. A single-byte Write takes
between 66 µs and 85 µs to complete. Programming an entire row using memory
Writes therefore takes no more than 21.8 ms. This duration of time does not
include time required by the CPU to transfer data to the registers, which is a func-
tion of the instructions employed and the system clock frequency.
The memory Write function does not support multibyte row programming.
Because memory Writes are self-timed, they can be performed back-to-back with-
out requiring polling or interrupts.
Erasing Flash Memory
Erasing bytes in Flash memory returns them to a value of FFh. Both the MASS
and PAGE ERASE operations are self-timed by the Flash controller, leaving the
CPU free to execute other operations in parallel. The DONE status bit in the Flash
Interrupt Control Register can be polled by software or used as an interrupt
source to signal completion of an Erase operation. If the CPU attempts to access
Flash memory while an erase is in progress, the Flash controller forces a wait
state until the Erase operation is completed.
Mass Erase
Performing a MASS ERASE operation on Flash memory erases all bits contained
in Flash, including the information page. This self-timed operation takes approxi-
mately 200 ms to complete.
Page Erase
The smallest erasable unit in Flash memory is a page. The pages to be erased,
whether they are the 128 main Flash memory pages or the information page, is
determined by the setting of the FLASH_PAGE register. This self-timed operation
takes approximately 10 ms to complete.
PS019209-0504
PRELIMINARY
Flash Memory