Chapter 10 XGATE (S12XGATEV3)
MC9S12XE-Family Reference Manual , Rev. 1.19
Freescale Semiconductor
385
10.8.2.5
Bit Field Operations
This addressing mode is used to identify the position and size of a bit field for insertion or extraction. The
width and offset are coded in the lower byte of the source register 2, RS2. The content of the upper byte is
ignored. An offset of 0 denotes the right most position and a width of 0 denotes 1 bit. These instructions
are very useful to extract, insert, clear, set or toggle portions of a 16 bit word
Figure 10-26. Bit Field Addressing
BFEXT
R3,R4,R5 ; R5: W4+1 bits with offset O4, will be extracted from R4 into R3
10.8.2.6
Special Instructions for DMA Usage
The XGATE offers a number of additional instructions for flag manipulation, program flow control and
debugging:
1. SIF: Set a channel interrupt flag
2. SSEM: Test and set a hardware semaphore
3. CSEM: Clear a hardware semaphore
4. BRK: Software breakpoint
5. NOP: No Operation
6. RTS: Terminate the current thread
10.8.3
Cycle Notation
show the XGATE access detail notation. Each code letter equals one XGATE cycle. Each
letter implies additional wait cycles if memories or peripherals are not accessible. Memories or peripherals
are not accessible if they are blocked by the S12X_CPU. In addition to this Peripherals are only accessible
every other XGATE cycle. Uppercase letters denote 16 bit operations. Lowercase letters denote 8 bit
operations. The XGATE is able to perform two bus or wait cycles per S12X_CPU cycle.
W4
O4
15
0
2
5
W4=3, O4=2
15
0
3
Bit Field Extract
Bit Field Insert
RS2
RS1
RD
0
3
4
7
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:
S12XE
products
in
208
MAPBGA
packages