DS31256 Maxim Integrated Products, DS31256 Datasheet - Page 125

• Manufacturer Part Number: DS31256
• Description: IC CTRLR HDLC 256-CHANNEL 256BGA
• Manufacturer: Maxim Integrated Products

Specifications of DS31256

• Controller Type: HDLC Controller
• Interface: Serial
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Supply: 500mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 256-BGA
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

9.3.5 DMA Configuration RAM
The device contains an on-board set of 1536 dwords (6 dwords per channel times 256 channels) that are
used by the host to configure the DMA and used by the DMA to store values locally when it is
processing a packet. Most of the fields within the DMA configuration RAM are for DMA use and the
host never writes to these fields. The host is only allowed to write (configure) to the lower word of
dword 1 for each HDLC channel. In
box.
Figure 9-21. Transmit DMA Configuration RAM
HDLC
Channel
1
HDLC
Channel
256
17D8h
17DCh
17F0h
17F4h
17F8h
17FCh
000h
004h
008h
00Ch
010h
014h
msb
31
dmatcram
Next Priority Pending Descriptor Pointer (16)
Next Priority Pending Descriptor Pointer (16)
unused (9)
unused (9)
Last Pending Descriptor Pointer (16)
Last Pending Descriptor Pointer (16)
Start Descriptor Pointer (16)
Start Descriptor Pointer (16)
unused (16)
unused (16)
PPP
PPP
PRI
ST(2)
PRI
ST(2)
Figure
Current Packet Data Buffer Address (32)
Current Packet Data Buffer Address (32)
PEND
ST(2)
PEND
ST(2)
Transmit DMA Configuration RAM
9-21, the host-configurable fields are denoted with a thick
EOF CV
EOF CV
125 of 183
Last Priority Pending Descriptor Pointer (16)
Last Priority Pending Descriptor Pointer (16)
Next Pending Descriptor Pointer (16)
Next Pending Descriptor Pointer (16)
Next Priority Descriptor Pointer (16)
Next Priority Descriptor Pointer (16)
Next Descriptor Pointer (16)
Next Descriptor Pointer (16)
Byte Count (13)
Byte Count (13)
Fields shown within the thick box
are written by the Host; all other
fields are for usage by the DMA and
can only be read by the Host
un-
used
un-
used
DQS
DQS
CH
EN
CH
EN
lsb
0