TMC424-PI24 Trinamic Microchips, TMC424-PI24 Datasheet - Page 11

• Manufacturer Part Number: TMC424-PI24
• Description: Economic Miniature Three Axis Microstepping Stepper Motor Controller
• Manufacturer: Trinamic Microchips

TMC428 DATASHEET (V. 2.00 / November 12, 2003)
6.4 Datagram Structure
The microcontroller (µC) communicates with the TMC428 via the four wire (nSCS_C, SCK_C, SDI_C,
SDO_C) serial interface. Each datagram sent to the TMC428 via the pin SDI_C and each datagram
received from the TMC428 via the pin SDO_C is 32 bits long. The first bit sent is the MSB (most
significant bit named sdi_c_bit#31 at Figure 6-1). The last bit sent is the LSB (least significant bit
named sdi_c_bit#0 in Figure 6-1). During reception of a datagram, the TMC428 immediately sends
back a datagram of the same length to the microcontroller. This datagram is the result of the request
from the microcontroller.
With each 32 bit wide datagram the microcontroller sends to the TMC428, it simultaneously receives a
32 bit wide datagram. A read request is distinguished from a write request by one datagram bit named
RW. The TMC428 immediately sends back requested read data in the lower 24 datagram bits. Status
bits are sent back in the higher 8 datagram bits. Datagrams sent from the microcontroller to the
TMC428 have the form:
3
1
The 32 bit wide datagrams sent to the TMC428 are assorted in four groups of bits: RRS (register RAM
select) selecting either registers or on-chip RAM; ADDRESS bits addressing memory within the
register set or within the RAM area; RW (read / not write (RW=1 : read / RW=0 : write)) bit
distinguishing between read access and write access; DATA bits for write access– for read access
these bits are don’t care and should be set to ‘0‘. Different internal registers of the TMC428 have
different lengths. So, for some registers only a subset of these 24 data bits is used. Unused data bits
should be set to ‘0‘ for clearness. Some addresses select more than a single register mapped together
into the 24 data bit space.
The 32 bit wide datagrams received by the µC from the TMC428 contain two groups of bits: STATUS
BITS and DATA BITS. The status bits, sent back with each datagram, carry the most important
information about internal states of the TMC428 and the settings of the reference switches. These
datagrams have the form:
3
1
Copyright © 2000–2003 TRINAMIC Microchips GmbH
3
0
3
0
STATUS BITS
2
9
2
9
SM3 SM2 SM1
ADDRESS
2
8
2
8
Table 6-4: 32 bit DATAGRAM structure received by µC (MSB received first)
2
7
2
7
Table 6-3 : 32 bit DATAGRAM structure sent from µC (MSB sent first)
32 bit DATAGRAM sent back from the TMC428 to µC via pin SDO_C
2
6
2
6
32 bit DATAGRAM sent from µC to the TMC428 via pin SDI_C
2
5
2
5
2
4
2
4
2
3
2
3
2
2
2
2
2
1
2
1
2
0
2
0
1
9
1
9
1
8
1
8
1
7
1
7
1
6
1
6
1
5
1
5
1
4
1
4
DATA BITS
1
3
1
3
DATA
1
2
1
2
1
1
1
1
1
0
1
0
9 8 7 6 5 4 3 2 1 0
9 8 7 6 5 4 3 2 1 0
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