MC68HC912B32 Datasheet, PDF (121/128 Pages) Motorola, Inc – 16-Bit Microcontroller

W/B — Word/Byte Transfer Flag
0 = Byte transfer
1 = Word transfer
BD/U — BDM Map/User Map Flag
Indicates whether BDM registers and ROM are mapped to addresses $FF00 to $FFFF in the standard
64-Kbyte address space. Used only by hardware read/write commands.
0 = BDM resources not in map
1 = BDM resources in map
INSTRUCTION — BDM Instruction Register (firmware command bit explanation)
(BDM) $FF00
Bit 7
6
5
4
3
2
1
Bit 0
H/F
DATA
R/W
TTAGO
REGN
The bits in the BDM instruction register have the following meanings when a firmware command is ex-
ecuted.
H/F — Hardware/Firmware Flag
0 = Firmware control logic
1 = Hardware control logic
DATA — Data Flag
0 = No data
1 = Data included in command
R/W — Read/Write Flag
0 = Write
1 = Read
TTAGO — Trace, Tag, Go Field
Table 45 TTAGO Decoding
TTAGO Value
00
01
10
11
Instruction
—
GO
TRACE1
TAGGO
REGN — Register/Next Field
Indicates which register is being affected by a command. In the case of a READ_NEXT or
WRITE_NEXT command, index register X is pre-incremented by two and the word pointed to by X is
then read or written.
Table 46 REGN Decoding
REGN Value
000
001
010
011
100
101
110
111
Instruction
—
—
READ/WRITE NEXT
PC
D
X
Y
SP
MC68HC912B32
MC68HC912B32TS/D
MOTOROLA
121