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Philips Semiconductors
Universal asynchronous receiver/transmitter (UART)
Table 2.
Register Bit Formats
Bit 7
Bit 6
MR1 (Mode Register 1)
RxRTS Control
RxINT Select
0 = no
0 = RxRDY
1 = yes
1 = FFULL
NOTE:
*In block error mode, block error conditions must be cleared by using the error reset command (command 4x) or a receiver reset.
MR2 (Mode Register 2)
Channel Mode
00 = Normal
01 = Auto echo
10 = Local loop
11 = Remote loop
NOTE: *Add 0.5 to values shown for 0–7 if channel is programmed for 5 bits/character.
CSR (Clock Select Register)
Receiver Clock Select
See Text
See Table 6 for BRG Test frequencies in this data sheet, and "Extended baud rates for SCN2681, SCN68681, SCC2691, SCC2692, SCC68681
and SCC2698B" Philips Semiconductors ICs for Data Communications, IC-19, 1994.
CR (Command Register)
Miscellaneous Commands
See Text
NOTE:
Access to the miscellaneous commands should be separated by 3 X1 clock edges. A disabled transmitter cannot be loaded.
SR (Channel Status Register)
Received Break
Framing
Error
0 = No
0 = No
1 = Yes
1 = Yes
*
*
NOTE:
*These status bits are appended to the corresponding data character in the receive FIFO. A read of the status register provides these bits [7:5]
from the top of the FIFO together with bits [4;0]. These bits are cleared by a reset error status command. In character mode they are reset when
the corresponding data character is read from the FIFO. In block error mode, block error conditions must be cleared by using the error reset
command (command 4x) or a receiver reset.
ACR (Auxiliary Control Register)
BRG Set
Select
0 = Set 1
1 = Set 2
ISR (Interrupt Status Register)
MPI Pin
MPI Pin
Change
Current State
0 = No
0 = Low
1 = Yes
1 = High
IMR (Interrupt Mask Resister)
MPI Change
MPI Level
Interrupt
Interrupt
0 = Off
0 = Off
1 = On
1 = On
2006 Aug 04
Bit 5
Bit 4
Error Mode*
Parity Mode
0 = Char
00 = With parity
1 = Block
01 = Force parity
10 = No parity
11 = Special mode
TxRTS
CTS Enable
Control
Tx
0 = No
0 = No
1 = Yes
1 = Yes
Parity
Overrun
Error
Error
0 = No
0 = No
1 = Yes
1 = Yes
*
Counter/Timer
Mode and Source
See Text
Not used
Counter
Ready
0 = No
1 = Yes
Not used
Counter
Ready Int
0 = Off
1 = On
Bit 3
Bit 2
Parity Type
0 = Even
1 = Odd
Stop Bit Length*
0 = 0.563
4 = 0.813
1 = 0.625
5 = 0.875
2 = 0.688
6 = 0.938
3 = 0.750
7 = 1.000
Transmitter Clock Select
See Text
Disable Tx
Enable Tx
0 = No
0 = No
1 = Yes
1 = Yes
TxEMT
TxRDY
0 = No
0 = No
1 = Yes
1 = Yes
Power-Down
Mode
0 = On
000 = RTSN
PWRDN Active
001 = C/TO
1 = Off
010 = TxC (1X)
Normal
011 = TxC (16X)
Delta
RxRDY/
Break
FFULL
0 = No
0 = No
1 = Yes
1 = Yes
Delta Break
RxRDY/FFULL
Interrupt
Interrupt
0 = Off
0 = Off
1 = On
1 = On
11
Product data sheet
SCC2691
Bit 1
Bit 0
Bits per Character
00 = 5
01 = 6
10 = 7
11 = 8
8 =1.563
C = 1.813
9 = 1.625
D = 1.875
A = 1.688
E = 1.938
B = 1.750
F = 2.000
Disable Rx
Enable Rx
0 = No
0 = No
1 = Yes
1 = Yes
FFULL
RxRDY
0 = No
0 = No
1 = Yes
1 = Yes
MPO Pin
Function Select
100 = RxC (1X)
101 = RxC (16X)
110 = TxRDY
111 = RxRDY/FFULL
TxEMT
TxRDY
0 = No
0 = No
1 = Yes
1 = Yes
TxEMT
TxRDY
Interrupt
Interrupt
0 = Off
0 = Off
1 = On
1 = On
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