Freescale Semiconductor MPC8260 - Manual (Page 756)

SCC BISYNC Mode
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
23-6 Freescale Semiconductor
The control character table lets the BISYNC controller recognize the end of the current block. Because the
controller imposes no restrictions on the format of BISYNC blocks, software must respond to received
characters and inform the controller of mode changes and of certain protocol events, such as resetting the
BCS. Using the control character table correctly allows the remainder of the block to be received without
interrupting software.
Up to eight control characters can be defined to inform the BISYNC controller that the end of the current
block is reached and whether a BCS is expected after the character. For example, the end-of-text character
(ETX) implies an end-of-block (ETB) with a subsequent BCS. An enquiry (ENQ) character designates an
end of block without a subsequent BCS. All the control characters are written into the data buffer. The
BISYNC controller uses a table of 16-bit entries to support control character recognition. Each entry
consists of the control character, an end-of-table bit (E), a BCS expected bit (B), and a hunt mode bit (H).
The RCCM entry defines classes of control characters that support masking option. The control character
table and RCCM are shown in
Figure 23-2 .
Table 23-4 describes control character table and RCCM fields.
Offset from
SCC x Base
0 1 2 3 7 8 15
0x42 E B H — CHARACTER1
0x44 E B H — CHARACTER2
0x46 E B H — CHARACTER3
0x48 E B H — CHARACTER4
0x4A E B H — CHARACTER5
0x4D E B H — CHARACTER6
0x4E E B H — CHARACTER7
0x50 E B H — CHARACTER8
0x52 1 1 1 — MASK VALUE(RCCM)
Figure 23-2. Control Character Table and RCCM