14.1.1 Command Format

The following frame format is used for commands where the host supports a DMA address of three bytes.

The first byte contains two fields:

The CMD/Data Start field indicates that this is a Command frame.
The CMD type field specifies the command to be executed.

The CMD type may be one of 15 commands:

DMA write
DMA read
Internal register write
Internal register read
Transaction termination
Repeat data packet
DMA extended write
DMA extended read
DMA single-word write
DMA single-word read
Soft Reset

The Payload field contains command specific data and its length depends on the CMD type.

The CRC field is optional and generally computed in software.

The Payload field can be one of four types each having a different length:

A: Three bytes
B: Five bytes
C: Six bytes
D: Seven bytes

Type A commands include:

DMA single-word RD
internal register RD
Transaction termination command
Repeat data PKT command
Soft Reset command

Type B commands include:

DMA RD Transaction
DMA WR Transaction

Type C commands include:

DMA Extended RD transaction
DMA Extended WR transaction
Internal register WR

Type D commands include:

DMA single-word WR

Full details of the frame format fields are provided in the following table:

Table 14-1. Frame Format Fields
Field	Size	Description
CMD Start	4 bits	Command Start: 4’b1100
CMD Type	4 bits	Command type: 4’b0001: DMA write transaction 4’b0010: DMA read transaction 4’b0011: Internal register write 4’b0100: Internal register read 4’b0101: Transaction termination 4’b0110: Repeat data Packet command 4’b0111: DMA extended write transaction 4’b1000: DMA extended read transaction 4’b1001: DMA single-word write 4’b1010: DMA single-word read 4’b1111: Soft Reset command
Payload	A: 3	The Payload field may be of Type A, B, C, or D Type A (length 3) *1- DMA single-word RD* Param: Read Address: Payload bytes: B0: ADDRESS[23:16] B1: ADDRESS[15:8] B2: ADDRESS[7:0] *2- internal register RD* Param: Offset address (two bytes): Payload bytes: B0: OFFSET-ADDR[15:8] B1: OFFSET-ADDR[7:0] B2: 0 *3- Transaction termination command* Param: none Payload bytes: B0: 0 B1: 0 B2: 0 *4- Repeat Data PKT command* Param: none Payload bytes: B0: 0 B1: 0 B2: 0 *5- Soft Reset command* Param: none Payload bytes: B0: 0xFF B1: 0xFF B2: 0xFF
Payload	B: 5	Type B (length 5) *1- DMA RD Transaction* Params: DMA Start Address: 3 bytes DMA count: 2 bytes Payload bytes: B0: ADDRESS[23:16] B1: ADDRESS[15:8] B2: ADDRESS[7:0] B3: COUNT[15:8] B4: COUNT[7:0] *2- DMA WR Transaction* Params: DMA Start Address: 3 bytes DMA count: 2 bytes Payload bytes: B0: ADDRESS[23:16] B1: ADDRESS[15:8] B2: ADDRESS[7:0] B3: COUNT[15:8] B4: COUNT[7:0]
Payload	C: 6	Type C (length 6) *1- DMA Extended RD transaction* Params: DMA Start Address: 3 bytes DMA extended count: 3 bytes Payload bytes: B0: ADDRESS[23:16] B1: ADDRESS[15:8] B2: ADDRESS[7:0] B3: COUNT[23:16] B4: COUNT[15:8] B5: COUNT[7:0] *2- DMA Extended WR transaction* Params: DMA Start Address: 3 bytes DMA extended count: 3 bytes Payload bytes: B0: ADDRESS[23:16] B1: ADDRESS[15:8] B2: ADDRESS[7:0] B3: COUNT[23:16] B4: COUNT[15:8] B5: COUNT[7:0]
Payload	C: 6	3- Internal register WR* Params: Offset address: 3 bytes Write data: 3 bytes * “clocked or clockless registers” Payload bytes: B0: OFFSET-ADDR[15:8] B1: OFFSET-ADDR [7:0] B2: DATA[31:24] B3: DATA [23:16] B4: DATA [15:8] B5: DATA [7:0]
Payload	D: 7	Type D (length 7) *1- DMA single-word WR* Params: Address: 3 bytes DMA Data: 4 bytes Payload bytes: B0: ADDRESS[23:16] B1: ADDRESS[15:8] B2: ADDRESS[7:0] B3: DATA[31:24] B4: DATA [23:16] B5: DATA [15:8] B6: DATA [7:0]
CRC7	1 byte	Optional data integrity field comprising two subfields: bit 0: fixed value ‘1’ bits 1-7: 7 bit CRC value computed using polynomial G(x) = X^7 + X^3 + 1 with seed value: 0x7F

The following table summarizes the different commands according to the payload type (DMA address = 3 bytes):

Table 14-2. Commands in Payload
Payload Type	Payload Size	Command Packet Size with CRC	Commands
Type A	3 bytes	5 bytes	1- DMA Single-Word Read 2- Internal Register Read 3- Transaction Termination 4- Repeat Data Packet 5- Soft Reset
Type B	5 bytes	7 bytes	1- DMA Read 2- DMA Write
Type C	6 bytes	8 bytes	1- DMA Extended Read 2- DMA Extended Write 3- Internal Register Write
Type D	7 bytes	9 bytes	1- DMA Single-Word Write