参数资料
型号: MC68HC05V7FN
厂商: MOTOROLA INC
元件分类: 微控制器/微处理器
英文描述: 8-BIT, MROM, 2.1 MHz, MICROCONTROLLER, PQCC68
封装: PLASTIC, LCC-68
文件页数: 23/170页
文件大小: 589K
代理商: MC68HC05V7FN
SECTION 15: MESSAGE DATA LINK CONTROLLER
MOTOROLA
Page 105
MC68HC05V7 Specification Rev. 1.0
15.3.2
RX BUFFERS
The Rx Buffers consist of two 11-byte arrays, with 8 bits per byte. Only one message may
occupy each Rx Buffer array at any time. Each Rx Buffer array has an internal register (the
’Rx Buffer pointer’) associated with it in which the length of the message body is recorded.
Following a reset, the MDLC has "possession" of the two empty Rx Buffers and their
associated Rx Buffer pointers are both reset to zero. Neither Rx Buffer appears in the CPU
memory map at this time, attempts to read them will return undefined data.
As each data byte of an incoming message is received by the MDLC, it is placed into the
next available entry of one of the Rx Buffers and the Rx Buffer pointer is incremented. This
continues until the end of the message is detected or an error occurs.
Figure 15-7:
MDLC Rx/Tx Buffers Outline
Rx Buffer
Array
#1
Rx Buffer
Array
#2
11 bytes
MRSR
MTCR
MUX
MDLC
Rx Logic
MDLC
Tx Logic
To
CPU
From
CPU
MDLC automatically
toggles multiplexer (MUX)
when one buffer is full.
Write to MRSR
"gives back" buffer
Indicates active path
Tx Buffer
Array
to MDLC for Rx.
Write to MTCR
"gives back" buffer
to MDLC for Tx.
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