UM0434 datasheet(367/390 Pages) STMICROELECTRONICS

367 / 390 page

Nexus3 module

UM0434

368/391

Initialize RWA using the Nexus register index of 0x9; see

Table 216. Configure as

shown below:

–

Write address = 0x

nnnn_nnnn (write address)

Initialize RWCS using the Nexus register index of 0x7; see

Table 216. Configure the

fields as shown in

Table 267:

Note:

Access count (CNT) of 0x0000 or 0x0001 performs a single access.

Initialize RWD using the Nexus register index of 0xA; see

Table 216. Configure as

shown below:

–

Write data = 0x

nnnn_nnnn (write data)

The Nexus block then arbitrates for the AHB system bus and transfers the data value

from the data buffer RWD register to the memory-mapped address in RWA. When the

access has completed without error (ERR=0), Nexus asserts the

nex_rdy_b signal (see

Table 271 for detail on nex_rdy_b) and clears RWCS[DV]. This indicates that the device

is ready for the next access.

Note:

Only the nex_rdy_b signal and the DV and ERR fields within RWCS provide read/write

access status to the external development tool.

12.10.2

Block write access (Non-Burst Mode)

For a non-burst block write access, follow Steps 1, 2, and 3 outlined in

Chapter 12.10.1:

Single write access on page 367,” to initialize the registers, but use a value greater than

one (0x0001) for RWCS[CNT].

The Nexus block then arbitrates for the AHB system bus and transfers the first data

value from the RWD register to the memory-mapped address in RWA. When the

transfer has completed without error (ERR = 0), the address from the RWA register is

incremented to the next word size (specified in RWCS[SZ]), 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.

Repeat step 3 in

Chapter 12.10.1: Single write access on page 367,” until the internal

CNT value is zero. When this occurs, RWCS[DV] is cleared to indicate the end of the

block write access.

Table 267.

Single write access field settings

Field

Setting

AC (Access control)

1 (indicates start access)

MAP (Map select)

000 (primary memory map)

PR (Access priority)

00 (lowest priority)

RW (Read/write)

1 (write access)

SZ (Word size)

nn (32-bit, 16-bit, 8-bit)

CNT (Access count)

0x0000 or 0x0001 (single access)

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