XC886/888CLM
Flash Memory
User’s Manual
4-11
V1.3, 2010-02
Flash Memory, V 1.0
4.5
Operating Modes
The Flash operating modes for each bank are shown in
Figure 4-8
Flash Operating Modes
In general, the Flash operating modes are controlled by the BSL and Flash
program/erase subroutines (see
).
Each Flash bank must be in ready-to-read mode before the program mode or sector(s)
erase mode is entered. In the ready-to-read mode, the 32-byte write buffers for each
Flash bank can be written and the memory cell contents read via CPU access. In the
program mode, data in the 32-byte write buffers is programmed into the Flash memory
cells of the targeted wordline.
The operating modes for each Flash bank are enforced by its dedicated state machine
to ensure the correct sequence of Flash mode transition. This avoids inadvertent
destruction of the Flash contents with a reasonably low software overhead. The state
machine also ensures that a Flash bank is blocked (no read access possible) while it is
being programmed or erased. At any time, a Flash bank can only be in ready-to-read,
program or sector(s) erase mode. However, it is possible to program/erase one Flash
bank while reading from another.
When the user sets bit PMCON0.PD = 1 to enter the system power-down mode, the
Flash banks are automatically brought to its power-down state by hardware. Upon
wake-up from system power-down, the Flash banks are brought to ready-to-read mode
to allow access by the CPU.
Ready-to-Read
Program
Sector(s) Erase
Power-Down
Call of
FLASH_ERASE routine
or by BSL
Call of
FLASH_PROG routine
or by BSL
System Power-Down
*