mpc823rg Freescale Semiconductor, Inc, mpc823rg Datasheet - Page 1206

• Manufacturer Part Number: mpc823rg
• Description: Mpc823 Powerquicc Integrated Communications Processor For Portable Systems
• Manufacturer: Freescale Semiconductor, Inc

eciwx
Assembler Syntax
Definition
Operation
Description
FIELD
FIELD
BIT
BIT
16
0
17
1
18
B
2
Freescale Semiconductor, Inc.
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3
else
EA
paddr
send load word request for paddr to device identified by
EAR[RID]
rD
devices in an alternative way. The MMU translation of the EA is
not used to select the special device, as it is used in most
instructions such as loads and stores. Rather, it is used as an
address operand that is passed to the device over the address
bus. Four other pins (the burst and size pins on the 60x bus) are
used to select the device; these four pins output the 4-bit
resource ID (RID) field that is located in the EAR register. The
eciwx instruction also loads a word from the data bus that is
output by the special device.
The eciwx instruction and the EAR register can be very efficient
when mapping special devices such as graphics devices that
use addresses as pointers.
EA is the sum (rA|0) + (rB).
A load word request for the physical address (referred to as real
address in the architecture specification) corresponding to EA is
sent to the device identified by EAR[RID], bypassing the cache.
The word returned by the device is placed in rD. EAR[E] must be
1. If it is not, a DSI exception is generated.
eciwx
External Control In Word Indexed
if rA = 0 then b
The eciwx instruction allows the system designer to map special
20
MPC823 REFERENCE MANUAL
4
word from device
b + (rB)
b
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address translation of EA
5
(rA)
rD,rA,rB
22
6
0
23
7
24
D
8
25
9
310
10
26
MPC823 Instruction Set—eciwx
11
27
12
28
13
29
A
14
30
B-53
15
31
0