re-bit dP program, it causes the microprocessor to en the DDCMP Maintenance Mode.
Itwill main in this mode untilinitialized. When this is "0" the microprocessor will enter
DDC~Normal Mode.
HDX - When set, half-duplex mode is selec ted lex When cleared
bythe program, full-dup mode is selected.
When set, a three second Start timer is select
ed;ted ing when clear, a one second Start timer is selec.
( the Start timer is the interval for send Start/Stack).
Reserved; Bit condition, set to O.
If selected for OOCMP Maintenance Mode, a special OOCMP message format, the maintenance message, is used for down-line loading, restarting, or otherwise maintaining satellite computer sys-tems. Messages in this format are subject to error checking but are unsequenced, unacknowledged, and not automatically retransmitted by the microprocessor.
To set the OMR II into Maintenance Mode, the user program must initialize the OM R I I. give it a Base In with the Resume bit clear, a Control In with the maintenance bit set, and set the half-duplex bit for HOX or clear for FOX.
In Maintenance Mode the OMR II provides the following functions:
I. Message framing.
2. Bit error detection - The header and data block check character (BCC) is checked by the OMRII. If the BCC is bad, the message is discarded with no notification given to the user program.
3. Link management - The OMRII provides proper line turn-around in half-duplex mode.
4. Some errors are recorded in the OMR II's internal RAM memory and are reported to the user program by updating the Base Table.
It is the responsibility of the user program to recover from any error via software time outs, since there is no retransmission attempted in maintenance mode.
3.3.3 Receive Buffer Address/Character Count In (RBA/CCI)
The RBA/CCI allows the user program to assign a receive buffer by giving the OM R II the starting address of the buffer and the character count in SEL 4 and SEL 6. The DMR II can accept up to 64 receive buffers.
START
..
START DMRDMR
-
-(HDX) START START (HDX)
1 SEC
- -
1 SECTIMER START
.. - -
START TIMERNO STACK RETURNED
START START
DMR
- -
DMR(HDX) START
- ---
(HDX)1 SEC ....
\ 3 SEC
TIMER ~STACK -/' TIMER
MK-2232
Figure 3-9 Start/Stack Sequence Timer
NOTE
DMCll can only accept a maximum of 7 buffers.
If the Resume feature is to be used, the maximum number of receive buffers is limited to eight. If the DMR II has more than eight buffers, it will only save up to eight after Resume. For example, if DMRII has BUF I, BUF 2, .... BUF 20 after a Shutdown/Resume operation, the OMRII will only retain BUF 1, BUF 2, .... BUF 8. The format for RBA/CCI is shown in Figure 3-10.
The starting address of the receive buffer is contained in SEL 4 and the two most significant bits of SEL 6. The buffer size is contained in the remaining bits of SEL 6. Buffers range from I to 16,383 bytes. The buffer size should be limited to a practical size large enough to accommodate the longest message expected. Each buffer corresponds to one OOCMP data message.
NOTE
The user program should give a higher priority to assigning all receive buffers before it assigns any transmit buffers. For example, if se)'en receive and seven transmit buffers are to be assigned, the pro-gram should assign all seven receive buffers before assigning any transmit buffers.
3.3.4 Transmit Buffer Address/Character Count In (TBA/CCI)
The TBA/CCI allows the user program to assign a transmit buffer by giving the OMR II the starting address of the buffer and the character count in SEL 4 and SEL 6. The OM R II can accept up to 64 transmit buffers.
NOTE
DMCll can only accept a maximum of seven buf-fers.
If the Resume feature is to be used, the maximum number of transmit buffers is limited to eight. If the DMRII has more than eight buffers, it will only save up to eight after Resume. For example, if OMRll has BUF 1, BUF 2, .... BUF 20 after a Shutdown/Resume operation, the OMRII will only retain BUF I, BUF 2, .... BUF 8. Buffers range from I to 16,383 bytes.
i i i
,
i BSELI I RECEIVE BAiCC IN
I I
0 1 0 0
I I I I I
0
I I I I I
I I I I
I I I I I
I I I I I
I I I I I 2
I I I I I I
, ,
T I,
I I
I
I II I
I I I I I I I 3
I I I I I I I
BUFFER ADDRESS LOW BYTE 4
I I I I I I I
BUFFER ADDRESS HIGH BYTE 5
I I I I I I I
CHARACTER COUNT LOW BYTE 6
I I i I I I I
I I
BA17 I BA16 I CHARACTER COUNT HIGH SIX BITS 7
, ,
I I I I I~_7 ___ ~ ___ 6 __ ~ __ 5 __ ~ __ 4 __ ~ __ 3 __ ~ __ 2 __ ~ ____ ~ __ ~
Figure 3-10 Receive Buffer Address/Character Count In Command Format
I SELO
I SEL
2ISEL4
ISEL6
MK-2224
The maximum size of the transmit buffer is a factor of the line speed and the reply or selection timer value. The time (T) required to transmit each buffer should be less than either the reply timer value (FDX) or the selection timer value (HDX). The user can optimize the buffer size using the following formula:
T = (Character Count
+
20) X 8 or Character = (T X Line Speed) - 20Line Speed Count 8
Where:
T
=
Seconds (should be less than the 3 second REP/Select Timer) Line Speed = Bits per second (b/s)Character Count = Number of bytes
Each buffer corresponds to one ODCMP data message. The format for this command is shown in Figure 3-11.
3.3.5 Halt Request Command
The Halt Request command format is shown in Figure 3-12.
I I
BUFFER ADDRESS HIGH BYTE
I I I I I
Figure 3-11 Transmit Buffer Address/Character Count In Command Format
3 transmission in progress.
The DMR 11 shutdown sequence is as follows:
1. Clear data terminal ready (DTR). This condition is performed only when a Halt Request command is issued.
It
does not occur during a fatal error shut-down.2. Return all queued up Control Outs.
3. Dump the Base Table to local CPU Memory. The DMRll will wait up to three seconds for data set ready (DSR) to clear, before issuing Control Out with Halt Complete.
4. Initialize the scratch pads and RAM location 0-400, and reset the M8203 line unit.
Data ports are not used for the Halt Request command.