Zilog Z16C30 - Manual (Page 107)

5-40
Z16C30 USC ®
U SER ' S M ANUAL
UM97USC0100
Z ILOG
5.20 COMMANDS
Commands are encoded values that software writes to a
register field to change the state of a channel or make it
perform some action. Typically commands don’t take any
software-perceptible time to perform. USC command fields
are write-only; reading them back may yield zeroes or
some unrelated status item.
Often commands represent a more compact and efficient
way to provide control features than dedicated register
bits. In fact, commands are so popular that each USC
channel includes three separate encoded command fields!
Figure 5-19 shows the Channel Command/Address Reg-
ister. Software can write various commands that affect the
Transmitter and/or the Receiver to its
RTCmd field
(CCAR15-11). In addition, software can write commands
that affect the Transmitter to the
TCmd field in the Transmit
Command/Status Register (TCSR15-12), and can write
commands that affect the Receiver to the
RCmd field in the
Receive Command/Status Register (RCSR15-12).
Writing all zeroes to any of the command fields does
nothing, which can be useful when the intent is to write to
other fields of the register. Zilog reserves other values not
listed below for future extensions to the USC family; such
values should not be written to the subject field.
RTCmd
Value
Function
00010 Reset Highest Serial IUS
00100 Trigger Channel Load DMA
00101 Trigger Rx DMA
00110 Trigger Tx DMA
00111 Trigger Rx and Tx DMA
01001 Purge Rx FIFO
01010 Purge Tx FIFO
01011 Purge Rx and Tx FIFO
01101 Load RCC
01110 Load TCC
01111 Load RCC and TCC
10001 Load TC0
10010 Load TC1
10011 Load TC0 and TC1
10100 Select Serial LSBit First
10101 Select Serial MSBit First
10110 Select D15-8 First
10111 Select D7-0 First
11001 Purge Rx
TCmd
Value
Function
0010 Clear Tx CRC Generator
0101 Select TICRHi=FIFO Status
0110 Select TICRHi=/INT Level
0111 Select TICRHi=/TxREQ Level
1000 Send Frame/Message
1001 Send Abort
1100 Enable DLE Insertion
1101 Disable DLE Insertion
1110 Clear EOF/EOM
1111 Set EOF/EOM
RCmd
Value
Function
0010 Clear Rx CRC Generator
0011 Enter Hunt Mode
0101 Select RICRHi=FIFO Status
0110 Select RICRHi=/INT Level
0111 Select RICRHi=/RxREQ Level
UM009402-0201