
PRODUCT SPECIFICATION
TMC22x5yA
69
Table 25. Serial Port Addresses
Data Transfer via Serial Interface
For each byte of data read or written, the MSB is the first bit; 
that is, bit 7 of the 8-bit sequence.
If the TMC22x5yA does not acknowledge the master device 
during a write sequence, the SDA remains HIGH so the mas-
ter can generate a stop signal. If the master device does not 
acknowledge the TMC22x5yA during a read sequence, the 
Decoder interprets this as “end of data.” The SDA remains 
HIGH so the master can generate a stop signal.
Writing data to specific control registers of the TMC22x5yA 
requires that the 8-bit address of the control register of inter-
est be written after the slave address has been established. 
This control register address is the base address for subse-
quent write operations. The base address autoincrements by 
one for each byte of data written after the data byte intended 
for the base address. If more bytes are transferred than there 
are available addresses, the address will not increment and 
remain at its maximum value of 3Fh. Any base address 
higher than 3Fh will not produce an ACKnowledge signal.
Data are read from the control registers of the TMC22x5yA 
in a similar manner. Reading requires two data transfer 
operations:
The base address must be written with the R/W\ bit of the 
slave address byte LOW to set up a sequential read 
operation. 
bit 7
A
6
(MSB)
1
1
1
1
1
1
1
1
bit 6
A
5
bit 5
A
4
bit 4
A
3
bit 3
A
2
(SA
2)
0
0
0
0
1
1
1
1
bit 2
A
1
(SA
1)
0
0
1
1
0
0
1
1
bit 1
A
0
(SA
0)
0
1
0
1
0
1
0
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Reading (the R/W bit of the slave address byte HIGH) 
begins at the previously established base address. The 
address of the read register autoincrements after each byte is 
transferred.
To terminate a write sequence to the TMC22x5yA, a stop 
signal must be sent. A stop signal comprises a LOW-to-
HIGH transition of SDA while SCL is HIGH. To terminate a 
read sequence simply do not acknowledge (NOACK) the last 
byte received and the TMC22x5yA will terminate the 
sequence.
A repeated start signal occurs when the master device driv-
ing the serial interface generates a start signal without first 
generating a stop signal to terminate the current communica-
tion. This is used to change the mode of communication 
(read, write) between the slave and master without releasing 
the serial interface lines. 
Serial Interface Read/Write Examples
Write to one control register
 Start signal
 Slave Address byte (R/W bit = LOW)
 Block Pointer (00)
 Base Address byte
 Data byte to base address
 Stop signal
Write to four consecutive XLUT locations
 Start signal
 Slave Address byte (R/W bit = LOW)
 Block Pointer (01)
 Base Address byte
 Data byte to base address
 Data byte to (base address + 1)
 Data byte to (base address + 2)
 Data byte to (base address + 3)
 Stop signal
Read from one XLUT location
 Start signal
 Slave Address byte (R/W bit = LOW)
Figure 35. Serial Port Read/Write Timing
t
BUFF
t
STAH
t
STASU
t
STOSU
t
DHO
t
DSU
t
DAL
t
BAH
SCL
SDA
65-22x5y-18