~ National ~ Semiconductor - Al Kossow's Bitsavers

7.0 CPU Registers (Continued)
BIT DEFINITION TABLE (Continued)
The following tables describe the location and function of all control and status bits in the various BCP addressable special
function registers. The Remote Interface Configuration register {RICl. which is addressable only by a remote system, is not
included.
CPU (for further information See Chapter on the CPU) (Continued)
Bit Name Location Reset State Function
Timer TLD Timer LoaD ACR [6] a Set high, to load timer. Cleared automatically when load
complete.
TM15-8 Timer TRH [7-0] XXXXXXXX Input/output port of high by1e of timer.
TM7-0 Timer TRL [7-0] XXXXXXXX Input/output port of low byte of timer.
TMC Timer Clock ACR [5] a Selects timer clock frequency. Must not be written when
Select
[TST] high. Can be written at same time as [TST] and
[TLD].
TMC Timer Clock
a CPU-CLK/16
1 CPU-CLK/2
TO Time Out Flag CCR [7] a Set high when timer counts to zero. Cleared by writing a 1 to
[TO] or by stopping the timer (by writing a a to [TST]).
TST Timer StarT ACR [7] a When high, timer is enabled and will count down from its
current value. Timer is stopped by writing a a to this location.
TRANSCEIVER
Table includes control and status bits only. It does not include definitions of bit fields provided for the formatting (de-formatting)
data frames. For further information see the Transceiver Section.
Bit Name Location Reset State Function
Transceiver LOOP Internal TMR [6] a When high, TX-ACT is disabled (held at 0) and transmitter
Control LOOP-back serial data is internally directed to the receiver serial data
input.
PS2-0 Protocol Select TMR [2-0] 000 Selects protocol for both transmitter and receiver.
PS2-0
Protocol
000 3270
001 3299 Multiplexer
010 3299 Controller
011 3299 Repeater
100 5250
101 5250 Promiscuous
1 1 a 8-bit
111 8-bit Promiscuous
RTF7-0 Receive/Transmit RTR [7-0] XXXXXXXX Input/output port of the least significant 8 bits of receive and
FIFOs
transmit FIFOs. [OWPl, [TF10-8] and [RTF1-0] are pushed
onto the transmit FIFO on moves to {RTR I. [RF10-8] and
[RTF7-0] are popped from receive FIFO on moves out of
{RTRI.
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