DMA Controller
Am186™CC/CH/CU Microcontrollers User’s Manual
8-39
Table 8-13
SmartDMA Transmit Channel Descriptor Format
Bit Number
Bit Name
Description
Transmit Buffer Address (Word 0)
15–0
LADR
1
Notes:
1. The address programmed in the LADR and HADR fields is a linear address, not a segment:offset address. For
example, if a transmit data buffer starts at segment address C000h and offset 1000h, it would be programmed as
follows:
Linear address= (segment address x 16) + offset address
= (C000h x 16) + 1000h = C1000h
LADR = 1000h
HADR = 0Ch
The LADR (Low Order) field contains the 16 low-order address bits of the data buffer
pointed to by this descriptor. The LADR field is written by the software and not changed
by the SmartDMA channel.
Transmit Buffer Status/Config (Word 1)
15
OWN
0 = Descriptor entry is owned by the software.
1 = Descriptor entry is owned by the SmartDMA channel.
The software sets the OWN bit after filling the buffer pointed to by this descriptor. The
SmartDMA channel clears the OWN bit (unless the TXS0 bit is set) after transmitting
the contents of the buffer. Neither the software nor the SmartDMA channel can alter
a descriptor entry after it has relinquished ownership.
14–10
Reserved
9
STP
The STP (Start of Packet) bit indicates that this is the first buffer to be used by the
SmartDMA channel for this packet. It is used to chain data buffers. The STP bit is set
by the software and is not changed by the SmartDMA channel. The STP bit must be
set in the first buffer of the packet, or the SmartDMA channel skips over this descriptor
and polls the next descriptor(s) until both the OWN and STP bits are set.
8
ENP
The ENP (End of Packet) bit indicates that this is the last buffer used by the SmartDMA
channel for this packet. It is used to chain data buffers. If both the STP and ENP bits
are set, the packet fits into one buffer and there is no data chaining. The ENP bit is
set by the software and is not changed by the SmartDMA channel.
7–0
HADR
The HADR (High Order) field contains the eight high-order address bits of the data
buffer pointed to by this descriptor. The highest four bits of the address must be set
to 0000b. These address bits do not exist in the microcontroller’s 20-bit address but
are provided for LANCE compatibility. The HADR field is written by the software and
not changed by the SmartDMA channel.
Transmit Buffer Byte Count (Word 2)
15
TTCE
0 = Disable TTC interrupt.
1 = Enable TTC interrupt.
This bit is used to enable the Transmit Terminal Count interrupt.
14–0
BCNT
The BCNT (Buffer Byte Count) field contains the length in bytes of the buffer pointed
to by this descriptor. This number is expressed in 2’s complement format and indicates
the number of bytes from this buffer that are transmitted by the SmartDMA channel.
This field is written by the software and not changed by the SmartDMA channel. For
example, if you want to transfer 64 bytes, take the number 64 (40h), complement it
(7FBFh), and increment it by 1 (7FC0h). Place this number (7FC0h) in the BCNT field.
Transmit Buffer Word 3: This word is used for receive channels only; the transmit channels do not write any status
to this word.
Содержание Am186 CC
Страница 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Страница 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Страница 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Страница 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Страница 39: ...Architectural Overview Am186 CC CH CU Microcontrollers User s Manual 1 15 Figure 1 6 32 Channel Linecard CH CC...
Страница 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Страница 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Страница 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Страница 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Страница 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...