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Special function registers
PRELIMINARY V1.8
9
.
TABLE 3.
Register bank select bits
7.4.
Accumulator (ACC)
This register provides one of the operands for most ALU operations. In the instruction
table it is denoted as “A”.
On reset this register returns 00 hex.
7.5.
B Register (B)
This register provides the second operand for multiply or divide instructions. Otherwise
it may be used as a scratch pad register.
On reset this register returns 00 hex.
7.6.
Memory Size Register (MSIZ)
The purpose of this register is to define the amount of available internal program
memory. The amount available is:
(MSIZ + 1)
× 256.
On reset this register returns 3F hex or 16K of internal program memory.
• 16K byte internal ROM
• A total of 512 bytes of on-chip data RAM:
•
256 bytes standard RAM
•
256 bytes of additional on-chip data memory accessible by the MOVX com-
mand (XRAM).
7.7.
Interrupts
- Two external interrupt input pins (IRQ1, IRQ2)
RS1
RS0
Register Bank Select
0
0
RB0. Registers from 00 - 07 hex.
0
1
RB1. Registers from 08 - 0F hex.
1
0
RB2. Registers from 10 - 17 hex.
1
1
RB3. Registers from 18 - 1F hex.
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