SD6830 Datasheet, PDF (7/34 Pages) AUK corp – 4BIT MICROCONTROLLER

SD6830
6.3 Data Memory (RAM)
Data memory is used to store various type of processing data. This consists of a 32-nibble,
which is organized into two files of 16 nibbles each. RAM addressing is indirectly
implemented by a two registers; H, L. It’s upper 1-bit register (H) selects one of two files
and its lower 4-bit register (L) selects one of 16 nibbles in the selected file.
REG H (1-bit)
REG L ( 4-bit )
PORT
F
Figure 6-2. Data Memory Map
6.4 Stack Register (SK)
Stack register is used to store return address and provide a particularly mechanism for
transferring control between programs. Two level hardware push/pop stacks are
manipulated by CAL, CALL, and RET instructions. CAL/CALL instructions push the current
program counter value, incremented by “1”, into stack level 1. Stack level 1 is
automatically pushed to level 2.
If more than two subsequent CAL/CALL are executed, only the most recent two return
addresses are stored. RET instruction load the contents of stack level 1 into the program
counter while stack level 2 gets copied into level 1. If more than two subsequent RET are
executed, the stack will be filled with the address previously stored in level 2.
KSI-W002-000
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