TXZ Family
Flash Memory
2018-06-05
93 / 120
Rev. 2.0
6.6.6. Common Operation Regardless of the Command
This section describes common operation under the boot program execution condition.
6.6.6.1. Serial Operation Mode Determination
The controller must send “0x86” on the 1
st
byte at the desired baud rate in Table 6.7. See “Figure 6.13 Serial
operation mode determination data”. If communication is impossible, please set lower baud rate.
Table 6.7 Setting of baud rate in Single boot mode (fc=10MHz, No error)
Baud Rate (Calculation)
<BRN>
<BRK>
9600 (9599)
65
57
19200 (19203)
32
29
38400 (38388)
16
46
57600 (57637)
10
10
62500 (62500)
9
0
76800 (76923)
8
55
115200 (115274)
5
37
128000 (127796)
4
7
Figure 6.13 Serial operation mode determination data
“Figure 6.13 Serial operation mode determination data” shows a flowchart of internal boot program. Using 32-bit
timer (T32A) with the time of tAB, tAC and tAD, the 1
st
byte of serial operation mode determination data “0x86”
after reset is provided.
In “Figure 6.14
Reception flowchart in serial operation mode”, the CPU monitors the level of the receive pin, and
obtains a timer value at the moment when the receive pin’s level is changed. Therefore, the timer values of tAB,
tAC and tAD have a margin of error. Note that if a transfer goes at a high baud rate, the CPU may not be able to
determine the level of receive pin.
Serial operation mode determination flowchart” shows that the serial operation mode is determined
by whether the time length of the receive pin is long or short. If the length is tAB ≤ tCD, the serial operation mode
is determined as UART mode. The time of tAD is used for whether the automatic baud rate setting is enabled or not.
If the length is tAB > tCD, the serial operation mode is not determined as UART mode. Note that timer values of
tAB, tAC and tAD have a margin of error as mentioned before. If the baud rate goes high but operation frequency is
low, each timer value becomes small. This may generate unexpected determination. (To prevent this problem, set
the UART in the programming routine again if necessary.)
For example, the serial operation mode may not be determined as UART mode even when the controller attempts to
tAC
tAD