Module Stop; Write Data Buffer Function; Tend Output - Renesas H8S/2368 Series Hardware Manual

7.7.2

Module Stop

When the MSTP13 bit in MSTPCRH is set to 1, the DMAC clock stops, and the module stop state
is entered. However, 1 cannot be written to the MSTP13 bit if any of the DMAC channels is
enabled. This setting should therefore be made when DMAC operation is stopped.
When the DMAC clock stops, DMAC register accesses can no longer be made. Since the
following DMAC register settings are valid even in the module stop state, they should be
invalidated, if necessary, before a module stop.
• Transfer end/break interrupt (DTE = 0 and DTIE = 1)
• TEND pin enable (TEE = 1)
• DACK pin enable (FAE = 0 and SAE = 1)
7.7.3

Write Data Buffer Function

When the WDBE bit of BCR in the bus controller is set to 1, enabling the write data buffer
function, external write cycles in dual address transfers or single address transfers are executed in
parallel with internal accesses (on-chip memory or internal I/O registers).
• Write data buffer function and DMAC register setting
If the setting of a register that controls external accesses is changed during execution of an
external access by means of the write data buffer function, the external access may not be
performed normally. Registers that control external accesses should only be manipulated when
external reads, etc., are used with DMAC operation disabled, and the operation is not
performed in parallel with external access.
• Write data buffer function and DMAC operation timing
The DMAC can start its next operation during external access using the write data buffer
function. Consequently, the DREQ pin sampling timing, TEND output timing, etc., are
different from the case in which the write data buffer function is disabled. Also, internal bus
cycles maybe hidden, and not visible.

TEND Output

TEND
TEND TEND
7.7.4
If the last transfer cycle is for an internal address, note that even if low-level output at the TEND
pin has been set, a low level may not be output at the TEND pin under the following external bus
conditions since the last transfer cycle (internal bus cycle) and the external bus cycle are executed
in parallel.
1. Write cycle with write buffer mode enabled
2. DMAC single address cycle for a different channel with write buffer mode enabled
3. Bus release cycle
Rev. 2.00, 05/03, page 271 of 820