DOC#: SP-AP-0774 (Rev. 0.2) Page 3 of 14
their default setting at power-up. The use of this interface is
optional. Clock device register changes are normally made at
system initialization, if any are required. The interface cannot
be used during system operation for power management
functions.
Data Protocol
The clock driver serial protocol accepts byte write, byte read,
block write, and block read operations from the controller. For
block write/read operation, access the bytes in sequential
order from lowest to highest (most significant bit first) with the
ability to stop after any complete byte is transferred. For byte
write and byte read operations, the system controller can
access individually indexed bytes. The offset of the indexed
byte is encoded in the command code described in Table 1.
The block write and block read protocol is outlined in Table 2
while Table 3 outlines byte write and byte read protocol. The
slave receiver address is 11010010 (D2h).
Table 1. Command Code Definition
Bit Description
7 0 = Block read or block write operation, 1 = Byte read or byte write operation
(6:0) Byte offset for byte read or byte write operation. For block read or block write operations, these bits should be '0000000'
Table 2. Block Read and Block Write Protocol
Block Write Protocol Block Read Protocol
Bit Description Bit Description
1Start 1Start
8:2 Slave address–7 bits 8:2 Slave address–7 bits
9 Write 9 Write
10 Acknowledge from slave 10 Acknowledge from slave
18:11 Command Code–8 bits 18:11 Command Code–8 bits
19 Acknowledge from slave 19 Acknowledge from slave
27:20 Byte Count–8 bits 20 Repeat start
28 Acknowledge from slave 27:21 Slave address–7 bits
36:29 Data byte 1–8 bits 28 Read = 1
37 Acknowledge from slave 29 Acknowledge from slave
45:38 Data byte 2–8 bits 37:30 Byte Count from slave–8 bits
46 Acknowledge from slave 38 Acknowledge
.... Data Byte /Slave Acknowledges 46:39 Data byte 1 from slave–8 bits
.... Data Byte N–8 bits 47 Acknowledge
.... Acknowledge from slave 55:48 Data byte 2 from slave–8 bits
.... Stop 56 Acknowledge
.... Data bytes from slave / Acknowledge
.... Data Byte N from slave–8 bits
.... NOT Acknowledge
.... Stop
Table 3. Byte Read and Byte Write Protocol
Byte Write Protocol Byte Read Protocol
Bit Description Bit Description
1Start 1Start
8:2 Slave address–7 bits 8:2 Slave address–7 bits
9Write 9Write
10 Acknowledge from slave 10 Acknowledge from slave
18:11 Command Code–8 bits 18:11 Command Code–8 bits
19 Acknowledge from slave 19 Acknowledge from slave
27:20 Data byte–8 bits 20 Repeated start
