Freescale Semiconductor e200z3 Reference Manual page 412

Nexus3/Nexus2+ Module
10.10.5 Block Read Access (Non-Burst Mode)
1. For a non-burst block read access, follow steps 1 and 2 outlined in
Access," to initialize the registers, but using a value greater than one (0x0001) for RWCS[CNT].
2. 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 has completed without error (ERR = 0), the address
from RWA is incremented to the next word size (specified in the SZ field), and the number from
the CNT field is decremented. Nexus then asserts the nex_rdy_b pin. This indicates that the device
is ready for the next access.
3. The data can then be read from RWD with the access method outlined in
"Nexus3/Nexus2+ Register Access Through JTAG/OnCE,"
see Table 10-7.
4. Repeat steps 3 and 4 in
this occurs, RWCS[DV] is set to indicate the end of the block read access.
10.10.6 Block Read Access (Burst Mode)
1. For a burst block read access, follow steps 1 and 2 outlined in
Access," to initialize the registers, using a value of four (double-words) for the CNT field and an
SZ field indicating 64-bit access in RWCS.
2. The Nexus block then arbitrates for the AHB system bus and the burst read data is transferred from
the AHB to the data buffer (RWD register). For each access within the burst, the address from the
RWA register is incremented to the next double-word, specified in the SZ field, and the number
from the CNT field is decremented.
3. When the entire burst transfer has completed without error (ERR=0), Nexus then asserts the
nex_rdy_b pin, and RWCS[DV] is set to indicate the end of the block read access.
4. The data can then be read from the burst data buffer (RWD register) with the access method
outlined in Section 10.5, "Nexus3/Nexus2+ Register Access Through JTAG/OnCE,"
Nexus register index of 0xA; see
5. Repeat step 3 until all double-word values are read from the buffer.
The data values must be shifted out 32-bits at a time, least significant bit
first, that is double-word read = two word reads from RWD.
The actual RWA and CNT values within RWCS are not changed when
executing a block read access, burst or non-burst. The original values can be
read by the external development tool at any time.
10-46
Section 10.10.4, "Single Read Access,"
Table 10-7.
NOTE
NOTE
e200z3 Power Architecture Core Reference Manual, Rev. 2
Section 10.10.4, "Single Read
Section 10.5,
using the Nexus register index of 0xA,
until the CNT value is zero. When
Section 10.10.4, "Single Read
Freescale Semiconductor
using the