H8SX1663 datasheet(362/1158 Pages) RENESAS

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Section 6 Bus Controller (BSC)

Rev.1.00 Jun. 07, 2006 Page 310 of 1102

REJ09B0294-0100

6.15.2

Write Data Buffer Function for Peripheral Modules

This LSI has a write data buffer function for the peripheral module access. Using the write data

buffer function enables peripheral module writes and on-chip memory or external access to be

executed in parallel. The write data buffer function is made available by setting the PWDBE bit in

BCR2 to 1. For details on the on-chip peripheral module registers, see table 6.34, Number of

Access Cycles for Registers of On-Chip Peripheral Modules in section 6.14, Internal Bus.

Figure 6.102 shows an example of the timing when the write data buffer function is used. When

this function is used, if an internal I/O register write continues for two cycles or longer and then

there is an on-chip RAM, an on-chip ROM, or an external access, internal I/O register write only

is performed in the first two cycles. However, from the next cycle onward an internal memory or

an external access and internal I/O register write are executed in parallel rather than waiting until

it ends.

On-chip

memory

read

Peripheral module write

Peripheral module address

Internal

address bus

Internal I/O

address bus

Internal I/O

data bus

Figure 6.102 Example of Timing when Peripheral Module

Write Data Buffer Function is Used

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