Nexus3/ Module
e200z3 Power Architecture Core Reference Manual, Rev. 2
Freescale Semiconductor
10-45
NOTE
The actual RWA and RWCS[CNT] values are not changed when executing
a block write access, burst or non-burst. The original values can be read by
the external development tool at any time.
10.10.4 Single Read Access
1. Initialize RWA with the access method outlined in
Section 10.5, “Nexus3/ Register
using the Nexus register index of 0x9; see
. Configure
as shown below:
— Read address = 0xnnnn_nnnn (read address)
2. Initialize RWCS with the access method outlined in
Section 10.5, “Nexus3/ Register
using the Nexus register index of 0x7; see
. Configure
the bits as shown in
NOTE
Access count (CNT) of 0x0000 or 0x0001 performs a single access.
3. The Nexus block then arbitrates for the AHB system bus and the read data is transferred from the
AHB to the RWD register. When the transfer is completed without error (ERR=0), Nexus asserts
the nex_rdy_b pin (see
for details on nex_rdy_b) and sets RWCS[DV]. This indicates
that the device is ready for the next access.
4. The data can then be read from RWD with the access method outlined in
“Nexus3/ Register Access Through JTAG/OnCE,”
using the Nexus register index of 0xA;
NOTE
Only the nex_rdy_b signal and the DV and ERR bits within RWCS provide
read/write access status to the external development tool.
Table 10-29. Single Read Access Parameter Settings
Parameter
Settings
Access control (AC)
1 (to indicate start access)
Map select (MAP)
000 (primary memory map)
Access priority (PR)
00 (lowest priority)
Read/write (RW)
0 (read access)
Word size (SZ)
0
nn (32-bit, 16-bit, 8-bit)
Access count (CNT)
0x0000 or 0x0001(single access)