MC908QY8CDWE Datasheet, PDF (33/232 Pages) Freescale Semiconductor, Inc – Addendum to MC68HC908QB8, rev. 3

FLASH Memory (FLASH)
2.6 FLASH Memory (FLASH)
The FLASH memory is intended primarily for program storage. In-circuit programming allows the
operating program to be loaded into the FLASH memory after final assembly of the application product.
It is possible to program the entire array through the single-wire monitor mode interface. Because no
special voltages are needed for FLASH erase and programming operations, in-application programming
is also possible through other software-controlled communication paths.
This subsection describes the operation of the embedded FLASH memory. The FLASH memory can be
read, programmed, and erased from the internal V_DD supply. The program and erase operations are
enabled through the use of an internal charge pump.
The minimum size of FLASH memory that can be erased is 64 bytes; and the maximum size of FLASH
memory that can be programmed in a program cycle is 32 bytes (a row). Program and erase operations
are facilitated through control bits in the FLASH control register (FLCR). Details for these operations
appear later in this section.
NOTE
An erased bit reads as a 1 and a programmed bit reads as a 0. A security
feature prevents viewing of the FLASH contents.⁽¹⁾
2.6.1 FLASH Control Register
The FLASH control register (FLCR) controls FLASH program and erase operations.
Bit 7
6
5
4
3
2
1
Bit 0
Read: 0
0
0
0
HVEN MASS ERASE PGM
Write:
Reset: 0
0
0
0
0
0
0
0
= Unimplemented
Figure 2-3. FLASH Control Register (FLCR)
HVEN — High Voltage Enable Bit
This read/write bit enables high voltage from the charge pump to the memory for either program or
erase operation. It can only be set if either PGM =1 or ERASE =1 and the proper sequence for
program or erase is followed.
1 = High voltage enabled to array and charge pump on
0 = High voltage disabled to array and charge pump off
MASS — Mass Erase Control Bit
This read/write bit configures the memory for mass erase operation.
1 = Mass erase operation selected
0 = Mass erase operation unselected
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult
for unauthorized users.
MC68HC908QB8 Data Sheet, Rev. 3
Freescale Semiconductor
31