![](http://datasheet.mmic.net.cn/30000/MC68HLC98JL3EIP_datasheet_2370416/MC68HLC98JL3EIP_28.png)
Memory
MC68HC908JL3E Family Data Sheet, Rev. 4
28
Freescale Semiconductor
During a subroutine call, the CPU uses two bytes of the stack to store the return address. The stack
pointer decrements during pushes and increments during pulls.
NOTE
Be careful when using nested subroutines. The CPU may overwrite data in
the RAM during a subroutine or during the interrupt stacking operation.
2.5 Flash Memory
This sub-section 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.
2.6 Functional Description
The Flash memory consists of an array of 4,096 or 1,536 bytes with an additional 48 bytes for user
vectors. The minimum size of Flash memory that can be erased is 64 bytes (a page); 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:
$EC00–$FBFF; user memory; 4,096 bytes; MC68H(R)C908JL3E/JK3E
$F600–$FBFF; user memory; 1,536 bytes; MC68H(R)C908JK1E
$FFD0–$FFFF; user interrupt vectors; 48 bytes
NOTE
An erased bit reads as 1 and a programmed bit reads as 0. A security
feature prevents viewing of the Flash contents.(1)
Device
Flash Memory Size
(Bytes)
Memory Address Range
MC68H(R)C908JL3E
4,096
$EC00—$FBFF
MC68H(R)C908JK3E
4,096
$EC00—$FBFF
MC68H(R)C908JK1E
1,536
$F600—$FBFF
Addr.
Register Name
Bit 7
654321
Bit 0
$FE08
Flash Control Register
(FLCR)
Read:
0000
HVEN
MASS
ERASE
PGM
Write:
Reset:
00000000
$FE09
Flash Block Protect
Register
(FLBPR)
Read:
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
Write:
Reset:
00000000
= Unimplemented
Figure 2-3. Flash I/O Register Summary
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the Flash difficult for
unauthorized users.