SCC Programming Reference
E-38
MC68360 USER’S MANUAL
MOTOROLA
E.3.1.2.6 Transparent Status Register (SCCS).
This 8-bit register is located at offset
$88C (SCC1), $89C (SCC2), and $8AC (SCC3)on D15-D8 of a 16-bit data bus. The SCCS
register reflects the current status of the CD and CTS lines as seen by the SCC.
CD—Carrier Detect Status Changed (valid only when the ENR bit is set and the receive
clock is running)
0 = CD is asserted.
1 = CD is not asserted.
CTS—Clear-To-Send Status Changed (valid only when the ENT bit is set and the transmit
clock is running)
0 = CTS is asserted.
1 = CTS is not asserted.
E.3.1.3 GENERAL AND TRANSPARENT PROTOCOL-SPECIFIC PARAMETER RAM.
Each SCC has 32 words of parameter RAM used to configure receive and transmit opera-
tion, store temporary parameters for the CP, and maintain counters. The first 14 words are
general parameters, which are the same for each protocol. The last 18 words are specific to
the protocol selected. The following subsections discuss the parameters that the user must
initialize to configure the transparent operation.
E.3.1.3.1 RFCR/TFCR—Rx Function Code/Tx Function Code.
This 16-bit parameter
contains the function codes of the receive data buffers and transmit data buffers. The user
must initialize the function codes (FC2-FC0) to a value less than 7.
E.3.1.3.2 MRBLR—Maximum Rx
Buffer Length.
This 16-bit parameter defines the maxi-
mum receiver buffer length for each of the eight receive buffer descriptors.
E.3.1.4 RECEIVE BUFFER DESCRIPTORS.
Each SCC has eight receive buffer descrip-
tors. Each buffer descriptor consists of four words as shown below. Reserved bits in regis-
ters should be written as zeros.
E.3.1.4.1 Receive BD Control/Status Word.
To initialize the buffer, the user should write
bits15-12 and clear bits1-0. The IMP clears bit 15 when the buffer is closed and sets bits 5-
0 depending on which error occurred.
7
—
6
—
5
—
4
—
3
—
2
—
1
0
CD
CTS
15
0
14
FC2
13
FC1
12
FC0
11
0
10
0
9
0
8
0
7
0
6
5
4
3
0
2
0
1
0
0
0
FC2
FC1
FC0
15
E
14
X
13
W
12
I
11
—
10
—
9
—
8
—
7
—
6
—
5
—
4
—
3
—
2
—
1
0
OFFSET + 0
OFFSET +2
OFFSET +4
OV
CD
DATA LENGTH
RX BUFFER POINTER
OFFSET +6