1 extension words as required, 2 command sequence diagrams, 2 command sequence diagrams -21 – Motorola ColdFire MCF5281 User Manual
Page 639: Figure 30-15
Debug Support
Freescale Semiconductor
30-21
30.5.3.1.1
Extension Words as Required
Some commands require extension words for addresses and/or immediate data. Addresses require two
extension words because only absolute long addressing is permitted. Longword accesses are forcibly
longword-aligned and word accesses are forcibly word-aligned. Immediate data can be 1 or 2 words long.
Byte and word data each requires a single extension word and longword data requires two extension words.
Operands and addresses are transferred most-significant word first. In the following descriptions of the
BDM command set, the optional set of extension words is defined as address, data, or operand data.
30.5.3.2
Command Sequence Diagrams
The command sequence diagram in
shows serial bus traffic for commands. Each bubble
represents a 17-bit bus transfer. The top half of each bubble indicates the data the development system
sends to the debug module; the bottom half indicates the debug module’s response to the previous
development system commands. Command and result transactions overlap to minimize latency.
15
10
9
8
7
6
5
4
3
2
0
Operation
0
R/W
Op Size
0
0
A/D
Register
Extension Word(s)
Figure 30-15. BDM Command Format
Table 30-18. BDM Field Descriptions
Bit
Name
Description
15–10
Operation Specifies the command. These values are listed in
9
0
Reserved, should be cleared.
8
R/W
Direction of operand transfer.
0 Data is written to the CPU or to memory from the development system.
1 The transfer is from the CPU to the development system.
7–6
Op Size
Operand data size for sized operations. Addresses are expressed as 32-bit absolute values. Note
that a command performing a byte-sized memory read leaves the upper 8 bits of the response
data undefined. Referenced data is returned in the lower 8 bits of the response.
Operand Size
Bit Values
00 Byte
8 bits
01 Word
16 bits
10 Longword
32 bits
11 Reserved
—
5–4
00
Reserved, should be cleared.
3
A/D
Address/data. Determines whether the register field specifies a data or address register.
0 Indicates a data register.
1 Indicates an address register.
2–0
Register Contains the register number in commands that operate on processor registers.
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3