13 DMA CONTROLLER (DMAC)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
13-5
DSINC[1:0] = 0x1: Address increment
After a transfer of a data unit specified with UNIT[2:0] is completed, the destination address is incremented
for the transferred data unit. The address that has been incremented during transfer does not return to the ini-
tial value.
CHEN: Channel enable (D3/1st word)
Enables or disables DMA transfers in each channel.
CHEN = 0: Transfer disabled
DMA transfers in the channel with this bit set to 0 are disabled.
CHEN = 1: Transfer enabled
DMA transfers in the channel are enabled. When triggered in this status, the DMAC starts DMA transfers
in that channel (unless the transfer pausing function is operating, triggered by a high-priority channel).
CHEN is cleared upon completion of the current transfer. When the RELOAD bit (D1/1st word) is set to 0,
this disables subsequent DMA transfers. When RELOAD is 1, CHEN will be replaced with RELOAD03 (D3/
reload data 0) by auto-reloading. Therefore, if RELOAD03 is set to 1, CHEN will be set to 1 again enabling
the DMAC to accept the subsequent DMA trigger without setting via software.
TM: Transfer mode (D2/1st word)
Sets the transfer mode (single transfer mode, successive transfer mode).
TM = 0: Single transfer mode
In this mode, a transfer operation invoked by one trigger is completed after transferring one data unit of
the size set in UNIT[2:0]. If a data transfer needs to be performed a number of times as set by the transfer
counter, an equal number of triggers are required.
TM = 1: Successive transfer mode
In this mode, one trigger performs data transfer a number of times as set by the transfer counter. The transfer
counter is decremented each time a unit data is transferred, and successive transfers end when the counter
reaches 0.
RELOAD: Auto-reload enable (D1/1st word)
Enables or disables the auto-reload function. The auto-reload function resets the initial value of control infor-
mation set in the auto-reload area (configured the same as the four words in the control table) in the control
table as soon as the transfer counter reaches 0. With this function, you can execute transfers with the new condi-
tions without resetting the initial value in the DMAC interrupt handler routine.
RELOAD = 0: Auto-reload disabled
Setting this bit to 0 disables the auto-reload function. Furthermore, the CHEN bit is set to 0 when the trans-
fer counter reaches 0, disabling subsequent DMA transfers. The control table retains the contents when the
transfer counter reaches 0.
RELOAD = 1: Auto-reload enabled
Setting this bit to 1 enables the auto-reload function. When the transfer counter reaches 0, the control infor-
mation stored in the auto-reload area is reset on the control table. The next trigger executes DMA transfer
with the new conditions set in the reload data.
Note: Control information (initial value) for the auto-reload area should be prepared in the application
program.
PTW: Pointer bit width (D0/1st word)
Sets the pointer size when pointer is selected for the source type (ST).
• PTW = 0: 16 bits
DMAC performs a 16-bit read from the specified source address to obtain the pointer.
• PTW = 1: 8 bits
DMAC performs an 8-bit read from the specified source address to obtain the pointer.