Chapter 5 Background Debug Controller (S12ZBDCV2)
S12ZVHY/S12ZVHL Family Reference Manual Rev. 1.05
148
Freescale Semiconductor
5.3.2.2
BDC Control Status Register Low (BDCCSRL)
Figure 5-4. BDC Control Status Register Low
(
BDCCSRL)
Read: BDC access only.
Write: Bits [7:5], [3:0] BDC access only, restricted to flag clearing by writing a “1” to the bit position.
Write: Bit 4 never. It can only be cleared by a SYNC pulse.
If ACK handshaking is enabled then BDC commands with ACK causing a BDCCSRL[3:1] flag setting
condition also generate a long ACK pulse. Subsequent commands that are executed correctly generate a
normal ACK pulse. Subsequent commands that are not correctly executed generate a long ACK pulse. The
first ACK pulse after WAIT or STOP have been set also generates a long ACK. Subsequent ACK pulses
are normal, whilst STOP and WAIT remain set.
Long ACK pulses are not immediately generated if an overrun condition is caused by the host driving the
BKGD pin low whilst a target ACK is pending, because this would conflict with an attempted host
transmission following the BKGD edge. When a whole byte has been received following the offending
BKGD edge, the OVRUN bit is still set, forcing subsequent ACK pulses to be long.
Unimplemented BDC opcodes causing the ILLCMD bit to be set do not generate a long ACK because this
could conflict with further transmission from the host. If the ILLCMD is set for another reason, then a long
ACK is generated for the current command if it is a BDC command with ACK.
Register Address: This register is not in the device memory map. It is accessible using BDC inherent addressing commands
7
6
5
4
3
2
1
0
R
WAIT
STOP
RAMWF
OVRUN
NORESP
RDINV
ILLACC
ILLCMD
W
Reset
0
0
0
0
0
0
0
0
Table 5-6. BDCCSRL Field Descriptions
Field
Description
7
WAIT
WAIT Indicator Flag
— Indicates that the device entered wait mode. Writing a “1” to this bit whilst in wait mode
has no effect. Writing a “1” after exiting wait mode, clears the bit.
0 Device did not enter wait mode
1 Device entered wait mode.
6
STOP
STOP Indicator Flag
— Indicates that the CPU requested stop mode following a STOP instruction. Writing a
“1” to this bit whilst not in stop mode clears the bit. Writing a “1” to this bit whilst in stop mode has no effect.
This bit can only be set when the BDC is enabled.
0 Device did not enter stop mode
1 Device entered stop mode.
5
RAMWF
RAM Write Fault
— Indicates an ECC double fault during a BDC write access to RAM.
Writing a “1” to this bit, clears the bit.
0 No RAM write double fault detected.
1 RAM write double fault detected.