GMS81C7216 Datasheet, PDF (27/121 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

GMS81C7208/7216
8.3 Data Memory
Figure 8-8 shows the internal Data Memory space available. Data
Memory is divided into four groups, a user RAM, control regis-
ters, Stack, and LCD memory.
0000_H
User Memory
(192 Bytes)
00BF_H
00C0_H
Control
00FF_H
Registers
0100_{H LCD display RAM}
011A_H ^{(27 Nibbles)}
011B_H
User Memory
or Stack Area
(229 Bytes)
PAGE0
PAGE1
01FF_H
Figure 8-8 Data Memory Map
User Memory
The both GMS81C7208/16 has 448 × 8 bits for the user memory
(RAM).
There are two page internal RAM. Page is selected by G-flag and
RAM page selection register RPR. When G-flag is cleared to “0”,
always page 0 is selected regardless of RPR value. If G-flag is set
to “1”, page will be selected according to RPR value.
G=0
RPR=1, G=1
Page 0
Page 1
Page 0: 00~FF_H
Page 1: 100~1FF_H
Control Registers
The control registers are used by the CPU and Peripheral function
blocks for controlling the desired operation of the device. There-
fore 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_H to 0FF_H.
Note that unoccupied addresses may not be implemented on the
chip. Read accesses to these addresses will in general return ran-
dom data, and write accesses will have an indeterminate 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 (SET1, CLR1). Do not use read-mod-
ify-write instruction. Use byte manipulation instruction, for
example “LDM”.
Example; To write at CKCTLR
LDM CKCTLR,#09H ;Divide ratio(÷16)
Stack Area
The stack provides the area where the return address is saved be-
fore a jump is performed during the processing routine at the ex-
ecution of a subroutine call instruction or the acceptance of an
interrupt.
When returning from the processing routine, executing the sub-
routine return instruction [RET] restores the contents of the pro-
gram counter from the stack; executing the interrupt return
instruction [RETI] restores the contents of the program 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 19.
Figure 8-9 RAM Page Configuration
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