UM0434 Datasheet, PDF (369/390 Pages) STMicroelectronics – The primary objective of this user’s manual is to describe

Nexus3 module
UM0434
Note:
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 Chapter 12.5:
Nexus3 register access through JTAG/OnCE on page 348,” using the Nexus register
index of 0xA; see Table 216.
Only the nex_rdy_b signal and the DV and ERR bits within RWCS provide read/write access
status to the external development tool.
12.10.5
Block read access (Non-Burst Mode)
1. For a non-burst block read access, follow steps 1 and 2 outlined in Chapter 12.10.4:
Single read access on page 369,” 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 Chapter 12.5:
Nexus3 register access through JTAG/OnCE on page 348,” using the Nexus register
index of 0xA, see Table 216.
4. Repeat steps 3 and 4 in Chapter 12.10.4: Single read access on page 369,” until the
CNT value is zero. When this occurs, RWCS[DV] is set to indicate the end of the block
read access.
12.10.6
Note:
Note:
Block read access (Burst Mode)
1. For a burst block read access, follow steps 1 and 2 outlined in Chapter 12.10.4: Single
read access on page 369,” 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 Chapter 12.5: Nexus3 register access through JTAG/OnCE on
page 348,” using the Nexus register index of 0xA; see Table 216.
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.
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