Zilog Z80380 - Manual (Page 198)

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Z380 ™
U SER ' S M ANUAL
DC-8297-03
Z ILOG
SETC
SET CONTROL BIT
SETC mode mode = LCK, LW, XM
Operation: if (mode = LCK) then begin
SR(1)
←
1
end
else if (mode = LW) then begin
SR(6)
←
1
end
else begin
SR(7)
←
1
end
When setting Lock mode (LCK), the LCK bit (bit 1) in the Select Register (SR) is set to 1,
disabling external bus requests. Note that bus requests are not disabled until after this
instruction has been executed, and that one or more of the succeeding instructions may also
have been fetched for decoding before this instruction has been executed.
When setting Long Word mode (LW), the LW bit (bit 6) in the SR is set to 1, selecting 32-bit
words. When using 32-bit words, all word load instructions transfer 32 bits.
When setting Extended mode (XM), the XM bit (bit 7) in the SR is set to 1, selecting addresses
modulo 4,294,967,296 (32 bits) as opposed to addresses modulo 65536 (16 bits) in Native
mode. In Extended mode CALL and RETurn instructions save and restore 32 bit PC values
to and from the stack, and the PC pushed to the stack in response to an interrupt is 32 bits.
In Extended mode, address manipulation instructions such as INCrement, DECrement,
ADD, and Jump Relative (JR) employ 32-bit addresses. Note that it is not possible to exit
from Extended mode except via reset.
Flags: S: Unaffected
Z: Unaffected
H: Unaffected
V: Unaffected
N: Unaffected
C: Unaffected
Addressing Execute
Mode Syntax Instruction Format Time Note
SETC mode 11mm1101 11110111 4
Field Encodings: mm: 01 for LW, 10 for LCK, 11 for XM