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SA-1100 Developer’s Manual 11-45
Peripheral Control Module
11.7.10 DMA Channel 2 Base and Current Address Registers
DMA channel 2’s base and current address registers (DBAR2 and DCAR2) function exactly like
DMA channel 1’s except that they are used exclusively for dual-panel operation. (See the preceding
sections.) When SDS=1, DMA channel 2 is used to supply frame buffer data to the lower half of the
display. Note that the palette buffer, which resides within the first 16 or 256 entries of the frame buffer,
is utilized only by DMA channel 1. The user should not place palette entries into the frame buffer for
DMA channel 2. The base address for channel 2 points to the first encoded pixel values for the lower
half of the display. For dual-panel operation, the user must perform the following sequence in order:
disable the LCD (LEN=0), program dual-panel mode (SDS= 0
→ 1), write the upper panel DMA base
address, write the lower DMA base address and enable the LCD (LEN= 0
→ 1). The following figures
show the format of these registers; question marks indicate that the values are unknown at reset.
Address: 0h B010 0018 DBAR2: DMA Channel 2 Base Address Register Read/Write
Bit 31302928272625242322212019181716
DMA Channel 2 Base Address Pointer
Reset????????????????
Bit1514131211109876543210
DMA Channel 2 Base Address Pointer
Reset????????????????
Bit Name Description
31..0 DBAR2
DMA channel 2 base address pointer.
Used to specify the base address of the frame buffer within off-chip memory for the lower
half of the display in dual-panel operation. Value in DBAR2 is transferred to current
address pointer register 2 when LCD is first enabled (LEN= 0 → 1) and when the current
address pointer value reaches the end-of-frame buffer. DBAR2 should be written only
when the LCD is disabled or immediately after an interrupt is generated by setting the
base address update status (BAU) bit. The base address must be on a quadword
boundary. The user must always write bits 0 through 3 to zero.
Address: 0h B010 001C DCAR2: DMA Channel 2 Current Address Register Read-Only
Bit 31302928272625242322212019181716
DMA Channel 2 Current Address Pointer
Reset????????????????
Bit1514131211109876543210
DMA Channel 2 Current Address Pointer
Reset????????????????
Bit Name Description
31..0 DCAR2
DMA channel 2 current address pointer.
Read-only register. Continuously reflects the current address that DMA channel 2 is
transferring from or will use in the next transfer. Base address register is transferred to
this register whenever the LCD is first enabled and when the current address is equal to
the calculated end address of the buffer.