Operation Explanation - Fujitsu MB91260B Series Hardware Manual

15.3

Operation Explanation

This section explains the operating mode and the instruction operation the
multiplication and addition macro.
■ Operating Mode
The action of the multiplication and addition macro is controlled by manipulating the DSP-CSR register.
The multiplication and addition macro can be one of the two states described below. When stopped, the
multiplication and addition macro starts program execution when "1" is written to GoDSP, or a GODSPSV
signal is inputted from the Servo Block. The registers and memory that can be accessed from CPU depend
on whether calculation is being executed or stopped.
Each of these states is described below.
• Stopped: The multiplication and addition macro is stopped. The command RAM (I-RAM), data RAM
• Running: The multiplication and addition macro is running.
*: Although access is disabled, R/W operations have the following effect:
Write: No effect (Nothing is written.)
Read: Indeterminate
■ Instruction Operation
When "1" is written to the GoDSP bit of the DSP-CSR register, the multiplication and addition macro begins
command execution from the current DSP-PC (program counter). (Operation is in parallel with CPU
operation)
Before execution, set the I-RAM and DSP-PC values. (DSP-CSR and DSP-PC can be set simultaneously.)
When multiplication and addition macro command execution starts, the following operation control is
performed.
• When the multiplication and addition macro executes an HLT command
the command is executed. At this time, DSP-PC stops pointing to the address following the HLT
command.
• When a JMP command or STR command is being executed, interrupt requests can be sent to the CPU.
(interrupt masking available)
• Use a conditional branching command referring to bits USR0 to USR2 of the DSP-CSR, to switch
program flow.
*: An HLT command is a JMP or STR command with the HLT bit set to "1".
CHAPTER 15 MULTIPLICATION AND ADDITION CALCULATOR
HltDSP = 1 or HLT
Stopped
RunDSP = 0
(X-RAM and Y-RAM), and all registers of the multiplication and addition macro can be
accessed from the CPU. Transit to this state by writing "1" to HltDSP or executing the
HLT command. The system is also initialized to this state when it is reset.
When "1" is written to the GoDSP bit while in stopped status, control transitions to this
state, and program execution starts from the current DSP-PC (program counter). Transit
to the stopped state, and halt program execution, by writing "1" to the HltDSP bit or
executing the HLT command. Only the DSP-CSR and the DSP-OT 0 to 7 register are
accessible from the CPU. (Access to other registers and RAM is disabled
RunDSP = 1
GoDSP = 1
Running
*
*
, transits to stopped state after
)
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