Samsung S3C2500B User Manual page 217

S3C2500B
Ethernet
Controller 0
Ethernet
Controller 1
AHB Bus Programmable Priority Register are HPRIF(Programmable Priority Register for Fixed) and HPRIR
(Programmable Priority Register for Round-Robin).
If system configuration register (0xF0000000) SYSCFG[0] = 0x1, the programmable fixed priority is run by
HPRIF register. Each Master has its own fixed priority index. For example, GDMA has the index 0. The reset
value of HPRIF register is 0x00543210. The first field of HPRIF[3:0] indicates the highest priority. So, the GDMA
has the highest AHB master when SYSCFG[0] = 0x1 and the HPRIF has the reset value. For example,
SYSCFG[0] = 0x1 and the HPRIF is 0x00432501, the fixed priority order from the highest to the lowest is
Ethernet Controller 0, General DMA, HDLC Controller 2, Ethernet Controller 1, HDLC Controller 0, and HDLC
Controller 1.
If system configuration register (0xF0000000) SYSCFG[0] = 0x0, the programmable round-robin priority is run by
HPRIR register. All AHB bus masters own their respective field position in HPRIR. The ratio of the bus occupancy
can be programmed by writing an arbitrary value on each field. The arbitrary value can be 0x0 to 0xF.
The ratio of the bus occupancy of the bus master in the first field is
(hprir0+1)/((hprir5+1)+(hprir4+1)+(hprir3+1)+(hprir2+1)+(hprir1+1)+(hprir0+1)). The reset value of HPRIR register
is 0x00000000. So each master has the same bus occupancy ratio when SYSCFG[0] = 0x0 and the HPRIR has
the reset value. For example, SYSCFG[0] = 0x0 and the HPRIR is 0x0011F001, the expected ratios of the bus
occupancy of the bus masters, General DMA, Ethernet Controller 0, Ethernet Controller 1, HDLC Controller 0,
HDLC Controller 1, and HDLC Controller 2, are 2/24, 1/24, 1/24, 16/24, 2/24, and 2/24, respectively.
Group A
TIC
Group B
General
DMA
HDLC
Controller 2
HDLC
Controller 1
HDLC
Controller 0
Figure 4-3. Priority Groups of S3C2500B
SYSTEM CONFIGURATION
Group C
ARM940T
4-5