Zilog Z08470 - Manual (Page 301)

UM008007-0715 Z80 Instruction Description
Z80 CPU
User Manual
289
RST p
Operation
(SP – 1) ← PCH, (SP – 2) ← PCL, PCH ← 0, PCL ← P
Op Code
RST
Operand
p
Description
The current Program Counter (PC) contents are pushed onto the external memory stack,
and the Page 0 memory location assigned by operand p is loaded to the PC. Program exe-
cution then begins with the op code in the address now pointed to by PC. The push is per-
formed by first decrementing the contents of the Stack Pointer (SP), loading the high-order
byte of PC to the memory address now pointed to by SP, decrementing SP again, and load-
ing the low-order byte of PC to the address now pointed to by SP. The Restart instruction
allows for a jump to one of eight addresses indicated in the following table. The operand p
is assembled to the object code using the corresponding T state.
Because all addresses are stored in Page 0 of memory, the high-order byte of PC is loaded
with
00h . The number selected from the p column of the table is loaded to the low-order
byte of PC.
p t
00h 000
08h 001
10h 010
18h 011
20h 100
28h 101
30h 110
38h 111
1 1 t 1 1 1