MEC1404 Datasheet, PDF (421/572 Pages) Microchip Technology – Keyboard and Embedded Controller Products for Notebook PC

MEC140X/1X
Note: Steps 3 thorough 7 should be completed as a contiguous sequence. If not the interface could be presenting
incorrect data when software thinks it is accessing a valid register read.
31.10.2 BC-LINK MASTER WRITE OPERATION
1. Software starts by checking the status of the BUSY bit in the BC-Link Status Register. If the BUSY bit is ‘0’, pro-
ceed. If BUSY is ‘1’, firmware must wait until it is ‘0’.
2. Software writes the address of the register to be written into the BC-Link Address Register.
3. Software writes the data to be written into the addressed register in to the BC-Link Data Register.
4. The write to the Data Register starts the BC_Link write operation. The Master state machine sets the BUSY bit.
5. The BC-Link Master Interface transmits the write request packet.
6. When the write request packet is received by the BC-Link companion, the CRC is checked and data is written to
the addressed companion register.
7. The companion sends an ACK if the write is completed. A time-out will occur approximately 16 BC-Link clocks
after the packet is sent by the Master state machine. If a time-out occurs, the state machine will set the BC_ERR
bit in the Status Register to ‘1’ approximately 48 clocks later and then clear the BUSY bit.
8. The Master state machine issues the Bit Clear interrupt and clears the BUSY bit after receiving the ACK from the
Companion
9. If a Bus Error occurs, firmware must issue a soft reset by setting the RESET bit in the Status Register to ‘1’.
10. The write can re-tried once BUSY is cleared.\
31.11 EC-Only Registers
The registers listed in the EC-Only Register Summary table are for a single instance of the BC-Link Master interface.
The addresses of each register listed in this table are defined as a relative offset to the host “Base Address” defined in
the EC-Only Register Base Address Table.
TABLE 31-3: EC-ONLY REGISTER BASE ADDRESS TABLE
Block Instance
BC-LINK
BC-LINK
Instance
Number
0
1
Host
EC
EC
Address Space
32-bit internal
address space
32-bit internal
address space
Base Address ()
0000_BC00h
0000_BD00h
The Base Address indicates where the first register can be accessed in a particular address space for a block instance.
TABLE 31-4: EC-ONLY REGISTER SUMMARY
Register Name
BC-Link Status Register
BC-Link Address Register
BC-Link Data Register
BC-Link Clock Select Register
EC Offset
00h
04h
08h
0Ch
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