GMS81508B HYNIX [Hynix Semiconductor], GMS81508B Datasheet - Page 27

• Manufacturer Part Number: GMS81508B
• Description: HYUNDAI MICRO ELECTRONICS 8-BIT SINGLE-CHIP MICROCONTROLLERS
• Manufacturer: HYNIX [Hynix Semiconductor]

GMS81508B/16B/24B
8.3 Data Memory
Figure 8-8 shows the internal Data Memory space availa-
ble. Data Memory is divided into four groups, a user RAM,
control registers, Stack, and LCD memory.
User Memory
The GMS815xxB has 448
(RAM).
Control Registers
The control registers are used by the CPU and Peripheral
function blocks for controlling the desired operation of the
device. Therefore these registers contain control and status
bits for the interrupt system, the timer/ counters, analog to
digital converters and I/O ports. The control registers are in
address range of 0C0
24
00BF
00C0
00FF
01FF
0100
0000
H
H
H
H
H
H
User Memory
User Memory
or Stack Area
Figure 8-8 Data Memory Map
Registers
Control
H
to 0FF
H
8 bits for the user memory
PAGE0
PAGE1
.
When “G-flag=1”
When “G-flag=0”,
this page is selected
Note that unoccupied addresses may not be implemented
on the chip. Read accesses to these addresses will in gen-
eral return random data, and write accesses will have an in-
determinate effect.
More detailed informations of each register are explained
in each peripheral section.
Note: Write only registers can not be accessed by bit ma-
nipulation instruction. Do not use read-modify-write instruc-
tion. Use byte manipulation instruction, for example “LDM”.
Example; To write at CKCTLR
Stack Area
The stack provides the area where the return address is
saved before a jump is performed during the processing
routine at the execution of a subroutine call instruction or
the acceptance of an interrupt.
When returning from the processing routine, executing the
subroutine return instruction [RET] restores the contents of
the program counter from the stack; executing the interrupt
return instruction [RETI] restores the contents of the pro-
gram counter and flags.
The save/restore locations in the stack are determined by
the stack pointed (SP). The SP is automatically decreased
after the saving, and increased before the restoring. This
means the value of the SP indicates the stack location
number for the next save. Refer to Figure 8-4 on page 20.
LDM
CLCTLR,#09H
HYUNDAI MicroElectronics
DEC. 1999 Ver 1.04
;Divide ratio( 32)