MC68HC58 Motorola, MC68HC58 Datasheet - Page 75

• Manufacturer Part Number: MC68HC58
• Description: Data Link Controller
• Manufacturer: Motorola

SBR — Status Byte Register
5.3.1 RFS[7:5] — Receive FIFO Status Field
5.3.1.1 Buffer Invalid or Empty
5.3.1.2 Buffer Contains More Than One Byte
5.3.1.3 Buffer Contains a Completion Code
5.3.1.4 Thirteenth Byte Received
MC68HC58
TECHNICAL DATA
RESET:
All information in the status byte is frozen while CS is asserted, and updated when CS
is negated.
This bit field shows the status of the RxFIFO buffer. When interrupts are enabled, RFS
can be used to determine the source of an interrupt request. Table 5-5 shows the
RxFIFO status encoding field. In the DLC, when the RFS bit field indicates that a com-
pletion code is at the head of the buffer, the accompanying data byte contains that
same completion code.
This value indicates that the accompanying data byte is not valid because the RxFIFO
buffer is empty or a flush frame command is being executed.
This value indicates that the RxFIFO buffer contains two to 12 bytes of data and no
completion code.
This value indicates that the RxFIFO buffer contains both data bytes and a completion
code. The completion code is not at the head of the buffer.
This value indicates that the RxFIFO buffer contains 12 bytes and a 13th byte has
been received. There is no completion code in the buffer.
7
0
Value
000
001
010
011
100
101
110
111
RFS
6
0
Table 5-5 RFS Field Encoding
Completion code at head of buffer, another frame available
Completion code at head of buffer, more bytes available
CONTROL AND STATUS CODES
Data byte in 13th buffer position, no completion code
5
0
Completion code only at head of buffer
Buffer contains more than one byte
Buffer contains a completion code
One data byte in buffer
Buffer invalid or empty
DLI
X
4
Description
NETF
3
0
4XMD
2
0
1
0
TMFS
MOTOROLA
0
0
5-9