xr
PRELIMINARY
XRT86VL38
REV. P1.0.6
OCTAL T1/E1/J1 FRAMER/LIU COMBO
126
T
ABLE
41: DMA 0 (W
RITE
) C
ONFIGURATION
R
EGISTER
R
EGISTER
24 DMA 0 W
RITE
C
ONFIGURATION
R
EGISTER
(DMA0 WCR) H
EX
A
DDRESS
: 0
X
n118
B
IT
F
UNCTION
T
YPE
D
EFAULT
D
ESCRIPTION
-O
PERATION
7
DMA0 RST
R/W
0
DMA_0 Reset
This READ/WRITE bit-field resets the transmit DMA (Write) channel 0.
0 = Normal operation.
1 = A zero to one transition resets the transmit DMA (Write) channel 0.
6
DMA0 ENB
R/W
0
DMA_0 Enable
This READ/WRITE bit-field enables the transmit DMA_0 (Write) inter-
face. After a transmit DMA is enabled, DMA transfers are only
requested when the transmit buffer status bits indicate that there is
space for a complete message or cell.
The DMA write channel is used by the external DMA controller to
transfer data from the external memory to the HDLC buffers within the
T1/E1 Framer. The DMA Write cycle starts by T1/E1 Framer asserting
the DMA Request (REQ0) ‘low’, then the external DMA controller
should drive the DMA Acknowledge (ACK0) ‘low’ to indicate that it is
ready to start the transfer. The external DMA controller should place
new data on the Microprocessor data bus each time the Write Signal is
Strobed low if the WR is configured as a Write Strobe. If WR is config-
ured as a direction signal, then the external DMA controller would
place new data on the Microprocessor data bus each time the Read
Signal (RD) is Strobed low.
0 = Setting this bit to ‘0’ disables the transmit DMA_0 (Write) interface
1 = Setting this bit to ‘1’ enables the transmit DMA_0 (Write) interface
5
WR TYPE
R/W
0
Write Type Select
This READ/WRITE bit-field selects the function of the WR signal.
0 = When this bit is set to ‘0’, WR functions as a direction signal (indi-
cates whether the current bus cycle is a read or write operation) and
RD functions as a data strobe signal.
1 =When this bit is set to ‘1’, WR functions as a write strobe signal
4 - 3 Reserved
-
-
Reserved
2
DMA0_CHAN(2)
R/W
0
Channel Select
These three READ/WRITE bit-fields select which T/E1 channel within
the XRT86VL38 uses the Transmit DMA_0 (Write) interface.
000 = Channel 0
001 = Channel 1
001 = Channel 2
011 = Channel 3
100 = Channel 4
101 = Channel 5
110 = Channel 6
111 = Channel 7
1
DMA0_CHAN(1)
R/W
0
0
DMA0_CHAN(0)
R/W
0