MC68HC908QY4CDW Datasheet, PDF (33/184 Pages) Freescale Semiconductor, Inc – Microcontrollers

FLASH Memory (FLASH)
2.6 FLASH Memory (FLASH)
This subsection describes the operation of the embedded FLASH memory. The FLASH memory can be
read, programmed, and erased from a single external supply. The program and erase operations are
enabled through the use of an internal charge pump.
The FLASH memory consists of an array of 4096 or 1536 bytes with an additional 48 bytes for user
vectors. 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. The address ranges for the user memory and vectors are:
• $EE00 – $FDFF; user memory, 4096 bytes: MC68HC908QY4 and MC68HC908QT4
• $F800 – $FDFF; user memory, 1536 bytes: MC68HC908QY2, MC68HC908QT2,
MC68HC908QY1 and MC68HC908QT1
• $FFD0 – $FFFF; user interrupt vectors, 48 bytes.
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.
Address: $FE08
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.
MC68HC908QY/QT Family Data Sheet, Rev. 6
Freescale Semiconductor
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