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SAB82525H-V21 参数 Datasheet PDF下载

SAB82525H-V21图片预览
型号: SAB82525H-V21
PDF下载: 下载PDF文件 查看货源
内容描述: 高层次的串行通信控制器扩展 [High-Level Serial Communication Controller Extended]
分类和应用: 通信控制器
文件页数/大小: 126 页 / 741 K
品牌: SIEMENS [ Siemens Semiconductor Group ]
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SAB 82525  
SAB 82526  
SAF 82525  
SAF 82526  
3.2 Half-Duplex SDLC-NRM Operation  
The LAP controllers of the two serial channels can be configured to function in a half-duplex  
Normal Response Mode (NRM), where they will operate as a slave (secondary) station, by  
setting the NRM bit in the XBCH register of the respective channel.  
In contrast to the full-duplex LAPB/LAPD operation, where the combined (primary +  
secondary) station transmits both commands and responses and may transmit data at any  
time, the NRM mode allows only responses to be transmitted and the secondary station may  
transmit only when instructed to do so by the master (primary) station.  
The HSCX gets the permission to transmit a frame from the primary by an S-, or I-frame with  
the poll bit (p) set!  
The NRM mode can be profitably used in a point-to-multipoint configuration with a fixed  
master-slave relationship and avoids collisions on the common transmit line. It’s the  
responsibility of the master station to poll the slaves periodically and to process the error  
recovery.  
Prerequisite for NRM operation is:  
auto-mode with 8-bit address field selected  
MODE: MDS0, MDS1, ADM = 000  
external timer mode  
MODE: TDM = 0  
same transmit and receive addresses, since only responses can be transmitted, i.e.  
XAD1 = XAD2 = RAL1 = RAL2 (address of secondary)  
Note: The broadcast address may be programmed in RAL2 if broadcasting is required.  
Reception of Frames  
The reception of frames functions equally to the LAPB/LAPD operation.  
Transmission of Frames  
The HSCX does not transmit S-, or I-frames if not instructed to do so by the primary station  
sending an S-, or I-frame with the poll bit set.  
The HSCX can be prepared to send an I-frame by the CPU issuing an XIF command (via  
CMDR) at any time. The transmission of the frame, however, will not be initiated by the HSCX  
prior to the reception of either a  
RR, or  
I-frame  
with a poll bit set (p = 1).  
After the frame has been transmitted (with the final bit set), the XFIFO is inhibited and the  
HSCX waits for the arrival of a positive acknowledgement.  
Semiconductor Group  
34  
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