MC908JL3ECPE Datasheet, PDF (28/180 Pages) Freescale Semiconductor, Inc – Microcontrollers

Memory
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.
Device
MC68H(R)C908JL3E
MC68H(R)C908JK3E
MC68H(R)C908JK1E
Flash Memory Size
(Bytes)
4,096
4,096
1,536
Memory Address Range
$EC00—$FBFF
$EC00—$FBFF
$F600—$FBFF
Addr.
$FE08
$FE09
Register Name
Read:
Flash Control Register
(FLCR)
Write:
Reset:
Flash Block Protect ^Read:
Register Write:
(FLBPR) _Reset:
Bit 7
0
0
BPR7
0
6
5
0
0
0
0
BPR6
BPR5
0
0
= Unimplemented
4
0
0
BPR4
0
3
HVEN
0
BPR3
0
Figure 2-3. Flash I/O Register Summary
2
MASS
0
BPR2
0
1
ERASE
0
BPR1
0
Bit 0
PGM
0
BPR0
0
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⁾
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the Flash difficult for
unauthorized users.
MC68HC908JL3E Family Data Sheet, Rev. 4
28
Freescale Semiconductor