IA8044/IA8344
SDLC COMMUNICATIONS CONTROLLER
Data Sheet
SMD Select Clock Mode Bits
SCM
2 1 0
Clock Mode
Data Rate
(Bits/sec)*
0 0 0 Externally clocked
0 – 2.4M**
0 0 1 Undefined
0 1 0 Self clocked, timer overflow
0 1 1 Undefined
244 – 62.5K
1 0 0 Self clocked, external 16X
1 0 1 Self clocked, external 32X
1 1 0 Self clocked, internal fixed
1 1 1 Self clocked, internal fixed
0 – 375K
0 – 187.5K
375K
187.5K
* based on a12 MHz crystal frequency
** 0 – 1M bps in loop configuration
Status/Command Register (STS):
The Status/Command register provides SIU control from and status to the CPU. The SIU can read
the STS and can write certain bits in the STS. The CPU can read and write the STS. Accessing the
STS by the CPU via 2 cycle instructions (JBC bit,rel and MOV bit,C) should not be used. STS is bit
addressable.
STS
Bit: 7
6
5
4
3
2
1
0
TBF
RBE
RTS
SI
BOV
OPB
AM
RBP
STS.0
STS.1
RBP
Receive buffer protect. When set prevents writing of data into
the receive buffer. Causes RNR response instead of RR in AUTO
mode.
Auto mode. Dual purpose bit depending upon the setting of bit NB
(SMD.1). If NB is cleared, AM selects the AUTO mode when
set, Flexible mode when clear. If NB is set, AM selects the addressed
mode when set and the non-addressed mode when clear. The SIU
can clear AM.
AM
STS.2
OPB
Optional poll bit. When set the SIU will AUTO respond to an
optional poll (UP with P=0). The SIU can set or clear the OPB.
Receive buffer overrun. The SIU can set or clear BOV.
SIU interrupt. This bit is set by the SIU and should be cleared
by the CPU before returning from the interrupt routine.
Request to send. This bit is set when the SIU is ready to
transmit or is transmitting. May be written by the SIU in AUTO
mode. RTS is only applied to the external pin in non-loop mode.
Can be thought of as a Transmit Enable. Note: RTS signal at the
pin (P1.6) is the inverted version of this bit.
STS.3
STS.4
BOV
SI
STS.5
RTS
Copyright 2003
innovASIC
ENG210010112-00
www.innovasic.com
Customer Support:
1-888-824-4184
The End of Obsolescence
Page 28 of 49
INNOVASIC [ INNOVASIC, INC ]
