ez80f91 ZiLOG Semiconductor, ez80f91 Datasheet - Page 107

• Manufacturer Part Number: ez80f91
• Description: Ez80 Acclaimplus!? Connectivity Assp Ez80f91 Assp
• Manufacturer: ZiLOG Semiconductor

PS027001-0707
Memory Read
Programming Flash Memory
Note:
A memory Read operation uses the address bus and data bus of the eZ80F91 device to
read a single data byte from Flash memory. This Read operation is similar to reads from
RAM. To perform Flash memory reads, the FLASH_CTRL register must be configured to
enable memory access to Flash with the appropriate number of wait states. See
on page 105.
Only the main area of Flash memory is accessible via memory reads. The information
page must be read using I/O access.
I/O Read
A single-byte I/O Read operation uses I/O registers for setting the column, page, and row
address to be read. A Read of the FLASH_DATA register returns the contents of Flash
memory at the designated address. Each access to the FLASH_DATA register causes an
autoincrement of the Flash address stored in the Flash address registers (FLASH_PAGE,
FLASH_ROW, FLASH_COL). To allow for Flash memory access time, the
FLASH_CTRL register must be configured with the appropriate number of wait states.
See
Flash memory is programmed using standard I/O or memory Write operations that the
Flash memory controller automatically translates to the detailed timing and protocol
required for Flash memory. The more efficient multibyte (row) programming mode is only
available via I/O Writes.
To ensure data integrity and device reliability, two main restrictions exist on programming
of Flash memory:
Single-Byte I/O Write
A single-byte I/O Write operation uses I/O registers for setting the column, page, and row
address to be written. The FLASH_DATA register stores the data to be written. While the
CPU executes an I/O instruction to load the data into the FLASH_DATA register, the
Flash controller asserts the internal WAIT signal to stall the CPU until the Flash Write
operation is complete. A single-byte Write takes between 66 µs and 85 µs to complete.
Programming an entire row (256 bytes) using single-byte Writes therefore takes no more
than 21.8 ms. This duration of time does not include the time required by the CPU to
transfer data to the registers which is a function of the instructions employed and the
system clock frequency. Each access to the FLASH_DATA register causes an
Table 38
1. The cumulative programming time since the last erase cannot
2. The same byte cannot be programmed more than once since the last erase.
exceed 31 ms for any given row.
on page 105.
Product Specification
eZ80F91 ASSP
Flash Memory
Table 38
99