M16C26 Datasheet, PDF (192/239 Pages) Renesas Technology Corp – 16-BIT CMOS SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/20 SERIES

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Preliminary Specifications Rev. 0.9
Specifications in this manual are tentative and subject to change.
CPU Rewrite Mode (Flash Memory Version)
M16C/26 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
CPU Rewrite Mode
The CPU rewrite mode is used to perform a read, program, or erase operation on the internal flash memory
under control by the central processing unit (CPU). There are two variations of this mode: erase write 0
mode (EW0) in which said operation is performed using a rewrite program residing in memory (i.e. RAM)
other than the internal flash memory and erase write 1 mode (EW1) in which said operation is performed
using the program residing in the internal flash memory.
In CPU rewrite mode, only the user ROM area shown in Figure 1.19.1 can be rewritten. The Program and
Block Erase commands can be executed only for the user ROM area in block intervals.
The EW0 mode control program must be stored in the user ROM area. In EW0 mode, because the flash
memory cannot be read from the CPU, the rewrite control program must be transferred to memory loca-
tions other than the internal flash memory before it can be executed.
The EW1 mode control program must be stored in the user ROM area. In this mode, the rewrite control
program does not have to be transferred to other memory locations before executing it. However, in this
mode, the block where the rewrite control program is stored cannot be operated on by the Program or
Erase commands.
User Mode and Boot Mode
The control program for CPU rewrite mode must be written into the user ROM area, in parallel I/O mode,
beforehand.
Normal user mode is entered when the microcomputer is reset with pulling CNVSS pin low. In this case,
the CPU starts operating using the control program in the user ROM area.
When the microcomputer is reset by pulling both the CNVSS and the P86 [CE] pins high, the CPU starts
operating using the standard serial I/O control program. This mode is called the “boot” mode. When reset
is deasserted in boot mode, be sure the P65 pin is not at high or the P67 pin is not at low.
Block Address
Block addresses refer to an even address of each block. These addresses are used in the block erase
command.
Outline Performance (CPU Rewrite Mode)
In the CPU rewrite mode, the CPU erases, programs and reads the internal flash memory as instructed by
software commands. There are two variations of this mode: erase write 0 mode (EW0) where operation is
executed in other than the internal flash memory such as the internal RAM and erase write 1 mode (EW1)
where operation is executed in the internal flash memory. One-wait must be set in both modes.
EW0 mode (CPU rewrite mode)
In this mode, the program must be executing out of RAM. The microcomputer is placed in EW0 mode by
setting the CPU rewrite mode select bit (address 01B716, bit 1) to 1, becoming ready to accept software
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