Freescale Semiconductor e200z3 Reference Manual page 409

10.10 Nexus3/Nexus2+ Read/Write Access to Memory-Mapped
Resources
The read/write access feature allows access to memory-mapped resources through the JTAG/OnCE port.
The read/write mechanism supports single as well as block reads and writes to e200z3 AHB resources.
The Nexus3/Nexus2+ module is capable of accessing resources on the e200z3 system bus, AHB, with
multiple configurable priority levels. Memory-mapped registers and other non-cached memory can be
accessed through the standard memory map settings.
All accesses are set up and initiated by the read/write access control/status register, RWCS, as well as RWA
and RWD.
Using RWCS, RWA and RWD, memory-mapped e200z3 AHB resources can be accessed through
Nexus3/Nexus2+. The following sections describe the steps that are required to access memory-mapped
resources.
Read/write access can only access memory-mapped resources when system
reset is de-asserted and clocks are running. Misaligned accesses are not
supported in the e200z3 Nexus3/Nexus2+ module.
10.10.1 Single Write Access
In the first three steps, the registers are initialized using the access method outlined in
"Nexus3/Nexus2+ Register Access Through JTAG/OnCE."
1. Initialize RWA using the Nexus register index of 0x9; see
— Write address = 0xnnnn_nnnn (write address)
2. Initialize RWCS using the Nexus register index of 0x7; see
shown in Table 10-28:
Access count (CNT) of 0x0000 or 0x0001 performs a single access.
Freescale Semiconductor
NOTE
NOTE
Table 10-28. Single Write Access Field Settings
Field
AC (Access control)
MAP (Map select)
PR (Access priority)
RW (Read/write)
SZ (Word size)
CNT (Access count)
NOTE
e200z3 Power Architecture Core Reference Manual, Rev. 2
Table 10-7. Configure as shown below:
Table 10-7. Configure the fields as
Setting
1 (indicates start access)
000 (primary memory map)
00 (lowest priority)
1 (write access)
0 nn (32-bit, 16-bit, 8-bit)
0x0000 or 0x0001 (single access)
Nexus3/Nexus2+ Module
Section 10.5,
10-43