Toshiba H1 Series - Manual (Page 98)

TMP92CZ26A
92CZ26A-95
(6) HDMAE (DMA Operation Enable Register)
The HDMAE register is used to enable or disable the DMAC operation.
Bits 0 to 5 correspond to channels 0 to 5. Unused channels should be set to “0”.
HDMAE Register
7 6 5 4 3 2 1 0
bit Symbol DMAE5 DMAE4 DMAE3 DMAE2 DMAE1 DMAE0
Read/Write R/W
After reset 0 0 0 0 0 0
Function
DMA channel operation
0: Disable
1: Enable
Note: Read-modify-write instructions can be used on this register.
Figure 3.6.7 HDMAE Register
(7) HDMATR (DMA Maximum Bus Occupancy Time Setting Register)
The HDMATR register is used to set the maximum duration of time the DMAC can
occupy the bus. The TMP92CZ26A does not have priority levels for bus arbitration.
Therefore, once the DMAC owns the bus, other masters (such as the LCDC) must wait until
the DMAC completes its transfer operation and releases the bus. This could lead to
problems in the system. For example, if the LCDC cannot own the bus as required, the LCD
display function may not work properly. To avoid such a situation, the DMAC limits the
duration of its bus occupancy by using this timer register. When the DMAC occupies the
bus for the duration of time set in this register, it releases the bus even if the specified DMA
operation has not been completed yet. After waiting for 16 states, the DMAC asserts a bus
request again to execute the rest of the DMA operation.
The DMAC counts the bus occupancy time regardless of which channel is occupying the
bus. To set the maximum bus occupancy time, ensure that the HDMAE register is set to
“00H” and set HDMATR to “1” and to the desired value.
Note: In case of using S/W start with HDMA, transmission start is to set to "1" DMAR
register. However DMAR register can't be used to confirm flag of transmission end. DMAR
register reset to "0" when HDMA release bus occupation once with HDMATR function.
HDMATR Register
7 6 5 4 3 2 1 0
bit Symbol DMATE DMATR6 DMATR5 DMATR4 DMATR3 DMATR2 DMATR1 DMATR0
Read/Write R/W
After reset 0 0 0 0 0 0 0 0
Function
Timer
operation
0: Disable
1: Enable
Maximum bus occupancy time setting
The value to be set in should be obtained by
“maximum bus occupancy time / (256/f
SYS
)”.
“00H” cannot be set.
Note: Read-modify-write instructions can be used on this register.
Figure 3.6.8 HDMATR Register
HDMAE
(097EH)
HDMATR
(097FH)