MC68000 MOTOROLA [Motorola, Inc], MC68000 Datasheet - Page 364

• Manufacturer Part Number: MC68000
• Manufacturer: MOTOROLA [Motorola, Inc]

MC68302 Applications
D-14
Set RXBD
* Set the last BD
*SCC1 Tx Buffer Descriptors Initialization values before execution
*00700440 5C00 0000 0003 0080 5C00 0000 0003 0090
*00700450 5C00 0000 0003 00A0 5C00 0000 0003 00B0
*00700460 5C00 0000 0003 00C0 5C00 0000 0003 00D0
*00700470 5C00 0000 0003 00E0 7C00 0000 0003 00F0
*
*
SetTXBD
*Set the last BD
***Prepare Tx Buffers: In this example each frame fits into one buffer ***
*00030080 0001 0203 0405 0607 0809 0A0B 0C0D 0E0F
*00030090 0001 0203 0405 0607 0809 0A0B 0C0D 0E0F
* . . .
*000300F0 0001 0203 0405 0607 0809 0A0B 0C0D 0E0F
NxtBF
NxtBT
MOVE.B
SUBQ.B
MOVE.W
MOVE.W
MOVE.L
ADDQ.L
ADDA.L
DBRA
MOVE.W
MOVE.W
MOVE.L
LEA.L
LEA.L
MOVE.W
MOVE.W
MOVE.L
SUBQ.B
MOVE.W
MOVE.W
MOVE.L
ADDQ.L
ADDA.L
DBRA
MOVE.W
MOVE.W
MOVE.L
LEA.L
MOVE.L
SUBO.B
CLR.L
MOVE.B
ADDQ.B
CMPI.B
#BD_CNT,D3
#2,D3
D1,ST_BD(A0)
#0,LN_BD(A0)
A1,PT BD(A0)
#SZ_BD,A0
#SZ_BF,A1
D3,SetRXBD
D2,ST_BD(A0)
#0,LN_BD(A0)
A1,PT_BD(A0)
TXBD_01,A0
TXBF_01,A1
#$5C00, D1
#$7C00,D2
#BD_CNT,D3
#$2,D3
D1,ST_BD(A0)
#0,LN_BD(A0)
A1,PT_BD(A0)
#SZ_BD,A0
#SZ_BF,A1
D3,SetTXBD
D2,ST_BD(A0)
#0,LN_BD(A0)
A1,PT_BD(A0)
TXBF_01,A0
#SZ_BD,D1
#1,D1
D2
D2,(A0)+
#$1,D2
#SZ_BF,D2
MC68302 USER’S MANUAL
;# of BD used = 8
;Set Control and Status Bits
;Length = 0
;Set buffer pointer
;Next BD
;Next BF
;Wrap = 1
;Length = 0
;Buffer Pointer
;A0 points to the first TXBD of SCC1
;A1 points to the first buffer
;D1 is used for setting the status of BD
;Ready = 0, External = 1, Interrupt = 1,
;Last = 1, TxCRC = 1
;D2 is for the last BD, Wrap = 1
;# of BD used = 8
;Count from 6 to 0
;Set Control and Status Bits
;Length = 0
;Set buffer pointer
;Next BD
;Next BF
;Wrap = 1
;Length = 0
;Buffer Pointer
;A1 points to the first buffer
;D1 is used to count the BD
;D2 is used as content and counter of BF
;Number of data in a buffer is 16
MOTOROLA