MC68EC040RC40A Freescale Semiconductor, MC68EC040RC40A Datasheet - Page 249

• Manufacturer Part Number: MC68EC040RC40A
• Description: IC MPU 32BIT 40MHZ 179-PGA
• Manufacturer: Freescale Semiconductor

Specifications of MC68EC040RC40A

• Processor Type: M680x0 32-Bit
• Speed: 40MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 179-PGA
• Lead Free Status / RoHS Status: Contains lead / RoHS Compliant
• Features: -

zeros, infinities, or NANs separately from normal data types. The floating-point condition
codes allow users to efficiently detect and handle these special values.
9.2.3.2 QUOTIENT BYTE. The quotient byte (see Figure 9-4) provides compatibility with
the MC68881/MC68882 FPU. This byte contains the seven least significant bits of the
unsigned quotient as well as the sign of the entire quotient.
The quotient bits can be used in argument reduction for transcendentals and other
functions. For example, seven bits are more than enough to determine the quadrant of a
circle in which an operand resides. The quotient field (bits 22–16) remains set until the
user clears it.
9.2.3.3 EXCEPTION STATUS BYTE. The EXC byte (see Figure 9-5) contains a bit for
each floating-point exception that can occur during the most recent arithmetic instruction
or move operation. The start of most operations clears this byte; however, operations that
cannot generate floating-point exceptions do not clear this byte. An exception handler can
use this byte to determine which floating-point exception(s) caused a trap.
9.2.3.4 ACCRUED EXCEPTION (AEXC) BYTE. The AEXC byte contains five exception
bits (see Figure 9-6) that the IEEE 754 standard requires for exception disabled
operations. These exceptions are logical combinations of the bits in the EXC byte. The
AEXC byte contains the history of all floating-point exceptions that have occurred since
the user last cleared the AEXC byte. In normal operations, only the user clears this byte
by writing to the FPSR; however, a reset or a restore operation of the null state can also
clear the AEXC byte.
MOTOROLA
SIGNALING NOT-A-NUMBER
OPERAND ERROR
BRANCH/SET ON
UNORDERED
OVERFLOW
23
S
BSUN
22
15
Freescale Semiconductor, Inc.
Figure 9-5. FPSR Exception Status Byte
For More Information On This Product,
Figure 9-4. FPSR Quotient Byte
SNAN
21
14
Go to: www.freescale.com
M68040 USER’S MANUAL
OPERR
20
13
QUOTIENT
OVFL
19
12
UNFL
18
11
17
DZ
10
SIGN OF QUOTIENT
SEVEN LEAST SIGNIFICANT
BITS OF QUOTIENT
INEX2
16
9
INEX1
8
INEXACT DECIMAL
INPUT
INEXACT OPERATION
DIVIDE BY ZERO
UNDERFLOW
9- 5