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2.0 Architectural Description

(Continued)

10 Round toward positive infinity. The nearest value which

is greater than or equal to the exact result is returned.

11 Round toward negative infinity. The nearest value which

is less than or equal to the exact result is returned.

Underflow Trap Enable (UEN):

Bit 3. If this bit is set, the

FPU requests a trap whenever a result is too small in abso-
lute value to be represented as a normalized number. If it is
not set, any underflow condition returns a result of exactly
zero.

Inexact Result Trap Enable (IEN):

Bit 5. If this bit is set,

the FPU requests a trap whenever the result of an operation
cannot be represented exactly in the operand format of the
destination. If it is not set, the result is rounded according to
the selected rounding mode.

2.1.2.2 FSR Status Fields

The FSR Status Fields record exceptional conditions en-
countered during floating-point data processing. The mean-
ings of the FSR status bits are given below:

Trap Type (TT):

bits 0-2. This 3-bit field records any excep-

tional condition detected by a floating-point instruction. The
TT field is loaded with zero whenever any floating-point in-
struction except LFSR or SFSR completes without encoun-
tering an exceptional condition. It is also set to zero by a
hardware reset or by writing zero into it with the Load FSR
(LFSR) instruction. Underflow and Inexact Result are always
reported in the TT field, regardless of the settings of the
UEN and IEN bits.

000 No exceptional condition occurred.

001 Underflow. A non-zero floating-point result is too small

in magnitude to be represented as a normalized float-
ing-point number in the format of the destination oper-
and. This condition is always reported in the TT field
and UF bit, but causes a trap only if the UEN bit is set. If
the UEN bit is not set, a result of Positive Zero is pro-
duced, and no trap occurs.

010 Overflow. A result (either floating-point or integer) of a

floating-point instruction is too great in magnitude to be
held in the format of the destination operand. Note that
rounding, as well as calculations, can cause this condi-
tion.

011 Divide by zero. An attempt has been made to divide a

non-zero floating-point number by zero. Dividing zero by
zero is considered an Invalid Operation instead (below).

100 Illegal Instruction. Two undefined floating-point instruc-

tion forms are detected by the FPU as being illegal. The
binary formats causing this trap are:

xxxxxxxxxx0011xx10111110

xxxxxxxxxx1001xx10111110

101 Invalid Operation. One of the floating-point operands of

a floating-point instruction is a Reserved operand, or an
attempt has been made to divide zero by zero using the
DIVf instruction.

110 Inexact Result. The result (either floating-point or inte-

ger) of a floating-point instruction cannot be represent-
ed exactly in the format of the destination operand, and
a rounding step must alter it to fit. This condition is al-
ways reported in the TT field and IF bit unless any other
exceptional condition has occurred in the same instruc-
tion. In this case, the TT field always contains the code
for the other exception and the IF bit is not altered. A
trap is caused by this condition only if the IEN bit is set;
otherwise the result is rounded and delivered, and no
trap occurs.

111 (Reserved for future use.)

Underflow Flag (UF):

Bit 4. This bit is set by the FPU when-

ever a result is too small in absolute value to be represented
as a normalized number. Its function is not affected by the
state of the UEN bit. The UF bit is cleared only by writing a
zero into it with the Load FSR instruction or by a hardware
reset.

Inexact Result Flag (IF):

Bit 6. This bit is set by the FPU

whenever the result of an operation must be rounded to fit
within the destination format. The IF bit is set only if no other
error has occurred. It is cleared only by writing a zero into it
with the Load FSR instruction or by a hardware reset.

2.1.2.3 FSR Software Field (SWF)

Bits 9-15 of the FSR hold and display any information writ-
ten to them (using the LFSR and SFSR instructions), but are
not otherwise used by FPU hardware. They are reserved for
use with NSC floating-point extension software.

2.2 INSTRUCTION SET

2.2.1 General Instruction Format

Figure 2-3 shows the general format of an Series 32000

instruction. The Basic Instruction is one to three bytes long

TL/EE/5234 – 6

FIGURE 2-3. General Instruction Format

6

Содержание NS32081-10

Страница 1: ... archi tecture and powerful addressing modes of the Series 32000 micro processor family Features Y Eight on chip data registers Y 32 bit and 64 bit operations Y Supports proposed IEEE standard for binary floating point arithmetic Task P754 Y Directly compatible with NS32016 NS32008 and NS32032 CPUs Y High speed XMOSTM technology Y Single 5V supply Y 24 pin dual in line package Block Diagram TL EE ...

Страница 2: ...t Instruction Set 2 3 Traps 3 0 FUNCTIONAL DESCRIPTION 3 1 Power and Grounding 3 2 Clocking 3 3 Resetting 3 0 FUNCTIONAL DESCRIPTION Continued 3 4 Bus Operation 3 4 1 Bus Cycles 3 4 2 Operand Transfer Sequences 3 5 Instruction Protocols 3 5 1 General Protocol Sequence 3 5 2 Floating Point Protocols 4 0 DEVICE SPECIFICATIONS 4 1 Pin Descriptions 4 1 1 Supplies 4 1 2 Input Signals 4 1 3 Input Output...

Страница 3: ...PackageÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ4 1 Timing Specification Standard Signal Valid After Clock Edge ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ4 2 Timing Specification Standard Signal Valid Before Clock Edge ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ4 3 Clock Timing ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ...

Страница 4: ...r positive or negative as shown in Table 1 2 TABLE 1 2 Sample E Fields E Field F Field Represented Value 011 110 100 0 1 5c2b1 e 0 75 011 111 100 0 1 5c20 e 1 50 100 000 100 0 1 5c21 e 3 00 Two values of the E field are not exponents 11 11 sig nals a reserved operand Section 2 1 3 00 00 repre sents the number zero if the F field is also all zeroes other wise it signals a reserved operand The S bit...

Страница 5: ... Point Unit FPU TL EE 5234 4 FIGURE 2 1 Register Set 2 1 1 Floating Point Registers There are eight registers F0 F7 on the NS32081 FPU for providing high speed access to floating point operands Each is 32 bits long A floating point register is referenced whenever a floating point instruction uses the Register ad dressing mode Section 2 2 2 for a floating point operand All other Register mode usage...

Страница 6: ...e this condi tion 011 Divide by zero An attempt has been made to divide a non zero floating point number by zero Dividing zero by zero is considered an Invalid Operation instead below 100 Illegal Instruction Two undefined floating point instruc tion forms are detected by the FPU as being illegal The binary formats causing this trap are xxxxxxxxxx0011xx10111110 xxxxxxxxxx1001xx10111110 101 Invalid ...

Страница 7: ...n the instruction which acts upon that variable Extraneous data movement is therefore mini mized Series 32000 Addressing Modes fall into nine basic types Register In floating point instructions these addressing modes refer to a Floating Point Register F0 F7 if the op erand is of a floating point type Otherwise a CPU General Purpose Register R0 R7 is referenced See Section 2 1 1 Register Relative A...

Страница 8: ...k memory disp SP SP0 or SP1 as selected in PSR 11010 Static memory disp SB 11011 Program memory adisp MEMORY RELATIVE 10000 Frame memory relative disp2 disp1 FP Disp2aPointer Pointer found at 10001 Stack memory relative disp2 disp1 SP address Disp1aRegister SP is 10010 Static memory relative disp2 disp1 SB either SP0 or SP1 as selected in PSR IMMEDIATE 10100 Immediate value None Operand is issued ...

Страница 9: ... indicates a choice of addressing mode expressions This choice affects the bina ry pattern in the corresponding gen1 or gen2 field of the instruction format Figure 2 6 Refer to Table 2 1 for the options available and their patterns Further details of the exact operations performed by each instruction are found in the Series 32000 Instruction Set Reference Manual Movement and Conversion The followi...

Страница 10: ...wer supply applied on pin 24 VCC See DC Electrical Characteristics table Grounding connections are made on two pins Logic Ground GNDL pin 12 is the common pin for on chip logic and Buffer Ground GNDB pin 13 is the common pin for the output drivers For optimal noise immunity it is recommend ed that GNDL be attached through a single conductor di rectly to GNDB and that all other grounding connection...

Страница 11: ...CTION PROTOCOLS 3 5 1 General Protocol Sequence Slave Processor instructions have a three byte Basic In struction field consisting of an ID byte followed by an Oper ation Word See Section 2 2 3 for FPU instruction encod ings The ID Byte has three functions 1 It identifies the instruction to the CPU as being a Slave Processor instruction 2 It specifies which Slave Processor will execute it 3 It det...

Страница 12: ...n The instructions are referenced by their mnemonics For the bit encodings of each instruction see Section 2 2 3 The Operand Class columns give the Access Classes for each general operand defining how the addressing modes are interpreted by the CPU see Series 32000 Instruction Set Reference Manual The Operand Issued columns show the sizes of the oper ands issued to the Floating Point Unit by the C...

Страница 13: ... the FPU to signal completion of an operation Section 3 5 1 Must be held high with an external pull up resistor while floating Data Bus D0 D15 16 bit bus for data transfer D0 is the least significant bit Section 3 4 4 2 ABSOLUTE MAXIMUM RATINGS Temperature Under Bias 0 C to a70 C Storage Temperature b65 C to a150 C All Input or Output Voltages with Respect to GND b0 5V to a7 0V Power Dissipation 1...

Страница 14: ...the input and output signals as illustrated in Figures 4 2 and 4 3 unless specifically stated otherwise ABBREVIATIONS L E Ð Leading Edge T E Ð Trailing Edge R E Ð Rising Edge F E Ð Falling Edge TL EE 5234 26 FIGURE 4 2 Timing Specification Standard Signal Valid After Clock Edge TL EE 5234 27 FIGURE 4 3 Timing Specification Standard Signal Valid Before Clock Edge 14 ...

Страница 15: ...ts Conditions tPWR 4 5 Power Stable to After VCC 50 50 ms RST R E Reaches 4 5V tRSTw 4 6 RST Pulse Width At 0 8V 64 64 tCLKp Both Edges tSs 4 7 Status ST0 ST1 Before SPC L E 50 33 ns Setup tSh 4 7 Status ST0 ST1 After SPC L E 40 35 ns Hold tDs 4 8 D0 D15 Setup Time Before SPC T E 40 30 ns tDh 4 8 D0 D15 Hold Time After SPC T E 50 35 ns tSPCw 4 7 SPC Pulse Width At 0 8V 70 50 ns from CPU Both Edges...

Страница 16: ...n Reset TL EE 5234 21 FIGURE 4 6 Non Power On Reset TL EE 5234 22 FIGURE 4 7 Read Cycle from FPU Note SPC pulse must be nominally 1 clock wide when writing into FPU TL EE 5234 23 FIGURE 4 8 Write Cycle to FPU Note SPC pulse may also be 2 clocks wide but its edges must meet the tSPCs and tSPCh requirements with respect to CLK 16 ...

Страница 17: ...PC Pulse from FPU TL EE 5234 25 FIGURE 4 10 RST Release Timing Note The rising edge of RST must occur while CLK is high as shown Physical Dimensions inches millimeters Ceramic Dual In Line Package D Order Number NS32081D 10 or NS32081D 15 NS Package Number D24C 17 ...

Страница 18: ...d in accordance support device or system or to affect its safety or with instructions for use provided in the labeling can effectiveness be reasonably expected to result in a significant injury to the user National Semiconductor National Semiconductor National Semiconductor National Semiconductor Corporation Europe Hong Kong Ltd Japan Ltd 1111 West Bardin Road Fax a49 0 180 530 85 86 13th Floor St...

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