10.0 Internal Registers
(Continued)
10.3 REGISTER DESCRIPTIONS
(Continued)
DATA CONFIGURATION REGISTER (DCR)
0EH (WRITE)
This Register is used to program the ST-NIC for 8- or 16-bit memory interface, select byte ordering in 16-bit applications and
establish FIFO thresholds.
The DCR must be initialized prior to loading the Remote Byte Count Registers. LAS is set on
power up.
7
6
5
4
3
2
1
0
Ð
FT1
FT0
ARM
LS
LAS
BOS
WTS
Bit
Symbol
Description
D0
WTS
Word Transfer Select
0: Selects byte-wide DMA transfers
1: Selects word-wide DMA transfers
; WTS establishes byte or word transfers for both Remote and Local DMA transfers
Note:
When word-wide mode is selected up to 32k words are addressable; A0 remains low.
D1
BOS
Byte Order Select
0: MS byte placed on AD15 – AD8 and LS byte on AD7 – AD0. (32xxx, 80x86)
1: MS byte placed on AD7 – AD0 and LS byte on AD15 – A8. (680x0)
; Ignored when WTS is low
D2
LAS
Long Address Select
0: Dual 16-bit DMA mode
1: Single 32-bit DMA mode
; When LAS is high, the contents of the Remote DMA registers RSAR0, 1 are issued as A16 – A31 Power up
high
D3
LS
Loopback Select
0: Loopback mode selected. Bits D1 and D2 of the TCR must also be programmed for Loopback operation
1: Normal Operation
D4
ARM
Auto-Initialize Remote
0: Send Command not executed, all packets removed from Buffer Ring under program control
1: Send Command executed, Remote DMA auto-initialized to remove packets from Buffer Ring
Note:
Send Command cannot be used with 680x0 byte processors.
D5
FT0
FIFO Threshold Select:
Encoded FIFO threshold. Establishes point at which bus is requested when filling or
emptying the FIFO. During reception, the FIFO threshold indicates the number of bytes (or words) the FIFO has
and
and
filled serially from the network before bus request (BREQ) is asserted.
D6
FT1
Note:
FIFO threshold setting determines the DMA burst length.
Receive Thresholds
FT1
FT0
Word Wide
Byte Wide
0
0
1 Word
2 Bytes
0
1
2 Words
4 Bytes
1
0
4 Words
8 Bytes
1
1
6 Words
12 Bytes
During transmission, the FIFO threshold indicates the number of bytes (or words) the FIFO has filled from the
Local DMA before BREQ is asserted. Thus, the transmission threshold is 13 bytes minus the received
threshold.
29
Obsolete