8-6
IIC
The following table provides a useful summary of how the IIC interface operates when some of the more
important bits are set in the control register.
Notes:
X
= don’t care
crnt
= current
Ack
= IIC “acknowledge” signal sent
Table 83. Control Register
Register ‘FF6X_0006’ - Control
bit 0
Halt master transfer. When set to a logic 1, the halt function is performed. If IIC was performing
a requested master transfer, it will issue the STOP signal at the earliest possible point on the IIC
bus. If no transfer was being done, then no action is taken on the bus. In either case, an interrupt
is activated if so enabled in the control registers. To halt a transfer, the pending transfer bit does
not need to be set to a logic 1.
bit 1
10/7 bit addressing. When set to a logic 1, 10-bit addressing is activated on the IIC bus. Slave
10-bit transfers are not controlled by this bit. Refer to the Hi slave address register. On a
requested master transfer, 10-bit addressing will be used to form the address on the IIC bus. A
logic 0 causes 7-bit addressing to be used.
bit 2
Count bit 0 (msb). The count bits indicate how many bytes are in the requested master transfer.
When all bytes have been successfully transferred, the requested transfer is considered
complete. The precise action taken is dependent upon the programming in this register and in
the mode control register.
bit 3
Count bit 1 (lsb)
bit 4
Repeated start. When set to a logic 1, the requested master transfer will be started using a
repeated START function on the IIC bus
bit 5
Chain. When set to a logic 1, the requested master transfer is one in a sequence of transfers.
Completion of the requested transfer only indicates that this piece of the transfer is complete.
The next action taken on the IIC bus is under the control of the program.
When set to a logic 0, the requested master transfer is either the only transfer to be performed at
this time or it is the last transfer in a sequence of transfers. In either case, completion of the
requested transfer causes a STOP condition to be sent on the IIC bus. A sequence of chained
transfers must end with a non-chained transfer of the same type. For example, a sequence of
chained write transfers must end with a non-chained write transfer, not a non-chained read
transfer.
bit 6
R/nW. When set to a logic 1, the requested master transfer is a read. When bit 1 equals a logic
0, a write is performed.
bit 7
Pending transfer. When set to a logic 1, a master transfer is started, if the IIC bus is free. The
type of requested transfer is specified by the other bits in this register. If the IIC bus is busy, then
IIC will wait for the bus to become free and will then start the requested transfer. This bit will be
cleared when the requested transfer is completed. When the transfer is complete, an interrupt, if
enabled in the mode control register, is activated.
Table 84. IIC Response to Control Settings
Bits in Control Register
Resulting action on the IIC bus and
inside the IIC Interface
Pending
Transfer
Chain
Repeated
Start
Halt
Master
Transfer
0
X
X
0
No action taken
1
1
0
0
Strt?, Xfr, Ack on last byte, pause
1
0
0
0
Strt?, Xfr, not Ack on last byte, stop
X
X
X
1
not Ack on crnt byte, stop
1
X
1
0
Strt?, Xfr, not Ack on last byte, wait
Summary of Contents for CPC700
Page 10: ...Table of Contents x Table of Contents...
Page 16: ...Tables xvi List of Tables...
Page 28: ...1 12 CPC700 User s Manual Preliminary...
Page 72: ...3 36 Processor Interface...
Page 132: ...4 60 Memory Controller...
Page 184: ...5 52 PCI Interface...
Page 194: ...6 10 Clock Power Management and Reset...
Page 224: ...8 18 IIC...
Page 244: ...10 10 Interrupt Controller...
Page 246: ...I 11 2 JTAG...
Page 250: ...12 4 Processor Local Bus PLB...
Page 262: ...14 10 Register Summary...
Page 267: ...CPC700 User s Manual Preliminary...