Table 30-7. fields and their positions in rm cells, 1 rm cell rate representation, Figure 30-15. rate format for rm cells – Freescale Semiconductor MPC8260 User Manual
Page 946: Figure 30-16. rate formula for rm cells, Rm cell rate representation -26, Rate format for rm cells -26, Rate formula for rm cells -26, Fields and their positions in rm cells -26

ATM Controller and AAL0, AAL1, and AAL5
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
30-26
Freescale Semiconductor
30.5.2.1
RM Cell Rate Representation
Rates in the RM cells are represented in a binary floating-point format using a 5-bit exponent (e), a 9-bit
mantissa (m), and a 1-bit nonzero flag (nz), as shown in
.
The rate (in cells/second) is calculated as in
Figure 30-16. Rate Formula for RM Cells
Initialize the traffic parameters (ER, MCR, PCR, or ICR) in the ABR protocol-specific connection tables
using the rate formula in
Table 30-7. Fields and their Positions in RM Cells
Fields
Octet
Bits
Description
Value
Header
1–5
All
ATM cell header
RM-VCC
PTI=6
ID
6
All
Protocol ID
1
DIR
7
0
Direction of RM cell (0 = forward, 1 = backward)
BN
7
1
Backward notification (BN = 0, the cell was generated by the source;
BN=1, the cell was generated by the network or by the destination)
CI
7
2
Congestion indication. (1 = congestion, 0 = otherwise)
NI
7
3
No increase indication. (1 = no increase allowed, 0 = otherwise)
RA
7
4
Not used (ATM Forum ABR)
0
—
7
5-7
Reserved, should be cleared.
0
ER
8–9
All
Explicit rate; see Section 30.5.2.1
CCR
10–11
All
Current cell rate; see Section 30.5.2.1
MCR
12–13
All
Minimum cell rate; see Section 30.5.2.1
QL
14–17
All
Not used (ATM Forum ABR)
0
SN
18–21
All
Not used (ATM Forum ABR)
0
—
22–51
All
Reserved, should be cleared.
0x6A for each byte
—
52
0–5
Reserved, should be cleared.
0
CRC-10
52
6–7
CRC-10
53
All
0
1
2
6
7
15
0
nz
Exponent
Mantissa
Figure 30-15. Rate Format for RM Cells
Ra te
2
e
1
m
512
----------
+
⎝
⎠
⎛
⎞
×
nz
Ч
=