Datasheet

Section 8 EXDMA Controller (EXDMAC)
R01UH0309EJ0500 Rev. 5.00 Page 475 of 1408
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
8.6 Usage Notes
(1) EXDMAC Register Access during Operation
Except for clearing the EDA bit to 0 in EDMDR, settings should not be changed for a channel in
operation (including the transfer standby state). Transfer must be disabled before changing a
setting for an operational channel.
(2) Module Stop State
When the MSTP14 bit is set to 1 in MSTPCRH, the EXDMAC clock stops and the EXDMAC
enters the module stop state. However, 1 cannot be written to the MSTP14 bit when any of the
EXDMAC’s channels is enabled for transfer, or when an interrupt is being requested. Before
setting the MSTP14 bit, first clear the EDA bit in EDMDR to 0, then clear the IRF or EDIE bit in
EDMDR to 0.
When the EXDMAC clock stops, EXDMAC registers can no longer be accessed. The following
EXDMAC register settings remain valid in the module stop state, and so should be changed, if
necessary, before making the module stop transition.
• ETENDE = 1 in EDMDR (ETEND pin enable)
• EDRAKE = 1 in EDMDR (EDRAK pin enable)
• AMS = 1 in EDMDR (EDACK pin enable)
(3) EDREQ Pin Falling Edge Activation
Falling edge sensing on the EDREQ pin is performed in synchronization with EXDMAC internal
operations, as indicated below.
[1] Activation request standby state: Waits for low level sensing on EDREQ pin, then goes to [2].
[2] Transfer standby state: Waits for EXDMAC data transfer to become possible, then goes to [3].
[3] Activation request disabled state: Waits for high level sensing on EDREQ pin, then goes to [1].
After EXDMAC transfer is enabled, the EXDMAC goes to state [1], so low level sensing is used
for the initial activation after transfer is enabled.