IBM PowerPC 405GP User Manual

Table 18·2. DMA Controller Configuration and Status Registers (continued)
Mnemonic DCRAddress Access Description Page
DMAO_DA2
Ox112 RIW DMA Destination Address Register 2 18-11
DMAO_SA2 Ox113 RIW DMA Source Address Register 2 18-10
DMAO_SG2 Ox114 RIW
DMA Scatter/Gather Descriptor Address Register 2
18-12
DMAO_CR3 Ox118 RIW
DMA Channel Control Register 3 18-8
DMAO_CT3 Ox119 RIW
DMA Count Register 3
18-11
DMAO_DA3
Ox11A
RIW
DMA Destination Address Register 3 18-11
DMAO_SA3 Ox11B
RIW
DMA Source Address Register 3 18-10
DMAO_SG3
Ox11C RIW
DMA Scatter/Gather Descriptor Address Register 3 18-12
DMAO_SR Ox120
R/Clear
DMA Status Register 18-7
DMAO_SGC
Ox123 RIW
DMA Scatter/Gather Command Register 18-13
DMAO_SLP
Ox12S RIW DMA Sleep Mode Register 18-6
DMAO_POL
Ox126 RIW
DMA Polarity Configuration Register 18-S
18.3.1 DMA Polarity Configuration Register (DMAO_POL)
The Polarity Configuration Register (DMAO_POL) is used to set the polarity (active state) of the
external DMA 1/0 signals: DMAReqn, DMAAckn, and EOTn[TCn]. As shown in Figure 18-2, if a bit in
DMAO_POL is zero, the corresponding signal is active high, otherwise the signal is active low.
Whenever any of the EOT polarities are changed (DMAO_POL[EnP), software must subsequently
clear the corresponding EOT status bits in the DMA Status Register (DMAO_SR[TSO:3]) prior to
enabling the associated DMA channel. This is necessary to prevent a channel from being disabled
because of an incorrect EOT status stored in the status bits.
ROP EOP A 1 P R2P E2P A3P
t + * + + +
1
0
111213141s16171819110111112
3
1
/
t t t t t t
AOP R1 P E1 P A2P R3P E3P
Figure 18·2. DMA Polarity Configuration Register (DMAO_POL)
0
ROP
DMAReqO Polarity
o DMAReqO is active high
1
DMAReqO is active low
1 AOP DMAAckO Polarity
o DMAAckO is active high
1
DMAAckO is active low
2
EOP EOTO[TCO] Polarity
o EOTO[TCO] is active high
1
EOTO[TCO] is active low
3
R1P DMAReq1
Polarity
o DMAReq1 is active high
1 DMAReq1 is active
low
Preliminary
Direct Memory Access Controller 18-S

IBM PowerPC 405GP Specifications

General

Brand	IBM
Model	PowerPC 405GP
Category	Computer Hardware
Language	English