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Successful Reply Format
For a success, the ACK bit will be set to 1. The number of reply messages generated depends on the amount of data requested. The final message will have the PF bit set to 1. All other reply messages will have the PF bit set to 0. Failure Reply Format
If the functional processor stops before generating the full set of data required by the COMBINATION command, a failure reply will be generated. The ACK bit will be set to 0, to distinguish this from a successful reply. The first byte of the return is the sequence state, as described in Table 32. The subsequent bytes contain the error message. This may be the ASIC ID message, or the result of the most recent warning or terminate message. If the error message would not fit into a single NSP packet it is truncated. Only one failure reply message will be generated, and the PF bit is set to 1. TIME (0x13) The TIME command returns the supervisors realtime clock, latched at the moment the final FEND character of the command is received. The data is returned as a 48-bit unsigned integer count of microseconds. The least significant bit of the count will always be zero, so the effective precision is 2 microseconds. The 48-bit count will roll over to zero after 17 years, in the unlikely event that a star tracker goes that long without resetting. By sending several TIME commands, separated by minutes or hours, an accurate comparison can be made between the star tracker clock and the spacecraft computer clock. Rev 4 star tracker clocks are not particularly accurate, and may benefit from calibration. Command Format
Reply Format
Protocol Layer 6 (Presentation Layer) Supervisor Mapping Memory Map Table 30: Supervisor Memory Map
The supervisor memory can be directly accessed with PEEK and POKE commands, and CRCs calculated with CRC commands. It is represented as a single 32-bit memory space, sparsely populated. The first 5.5 kB of program memory contain the bootloader. These are protected against POKEs so that the bootloader cannot be accidentally changed. The next 58.5 kB contains the supervisor application program. A sequence of POKE commands in bootloader mode can be used to load new application programs. The bootloader memory cannot be read by the application program, and so PEEK or CRC commands to those regions will fail if not in bootloader mode. Starting at address 0x00010000 is a 56 kB bootloader image for the functional processor. The first four bytes indicate the length of the program, and the first actual program byte lives at address 0x00001004. When a GO command is received to boot the functional processor from supervisor flash, the byte from 0x00001004 on the supervisor is loaded into byte 0x40200000 of the functional processor. Successive bytes from the supervisor are loaded into successive locations in the functional processor. When all of the bytes (indicated by the length field at the start) have been loaded the functional processor begins execution at address 0x40200000. The supervisor processor has two RAM areas. There is little need for a user to touch these. There are four banks of Special Function Registers (SFRs). These should not be POKEd without knowing exactly what is going on. Even PEEKing some of these registers can have unexpected side effects. Diagnostics Table 31: Diagnostic Channels
Each diagnostic channel is presented as a 32-bit unsigned integer. The internal storage for many of these is only 16 bits, so overflows may occur after 64k counts. Internal errors represent bad NSP events on the communications link between the supervisor and functional processors. External errors represent bad NSP events on the communiations link between the supervisor and the host spacecraft. Reset will clear all of the error counters. Reset Reason The reset reason is an enumerated type, describing the reason for the most recent reset of the supervisor processor. Table 32: Reset Reason Codes
Reset Count The reset count contains the number of supervisor processor resets since the last power cycle reset. Immediately after a power cycle the reset count will read as 0. After the first non-power-cycle reset it will read 1. Date: 2015-12-17; view: 592
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