ez80190 ZiLOG Semiconductor, ez80190 Datasheet - Page 134

• Manufacturer Part Number: ez80190
• Description: Ez80190 Microprocessor
• Manufacturer: ZiLOG Semiconductor

PS006613-0306
4. Write the fourth byte to the MACC Accumulator
5. Write the most significant byte to the MACC Accumulator
In Example 2, notice that the upper 3 bits of the final write are ignored.
OUT_SHIFT Function
The OUT_SHIFT field, bits 5:3 of the MACC_CTL register, defines the magnitude
of the right-shift that is performed when the CPU reads a result from the MACC
Accumulator registers MACC_AC0, MACC_AC1, MACC_AC2, MACC_AC3, and
MACC_AC4. The MACC automatically manipulates the shift of the 40-bit value as
it is read as a succession of 8-bit values. The READs can be right-shifted 0 to 7
bits depending upon the value of OUT_SHIFT. Because the MACC Accumulator
value is a two’s-complement value, the upper bits are filled with copies of the sign
bit, bit 39, during the right-shift operation.
Example 1. When OUT_SHIFT =
ters are not shifted. If the 40-bit MACC Accumulator value is read using a succes-
sion of 8-bit READs, the procedure appears as follows:
1. Read the least significant byte from the MACC Accumulator
2. Read the second byte from the MACC Accumulator
3. Read the third byte from the MACC Accumulator
4. Read the fourth byte from the MACC Accumulator
5. Read the most significant byte from the MACC Accumulator
Example 2. When OUT_SHIFT =
isters are right-shifted by 3 bits. The 3 most significant bits are filled with copies of
the most significant bit of the 40-bit MACC Accumulator. In this example, assume
the MACC Accumulator currently contains a positive number so that the most sig-
MACC Accumulator [34:27] = MACC_AC3[7:0] = DATA_IN[7:0]
MACC Accumulator [39:35] = MACC_AC4[4:0] = DATA_IN[4:0]
DATA_OUT[7:0] = MACC_AC0[7:0] = MACC Accumulator [7:0]
DATA_OUT[7:0] = MACC_AC1[7:0] = MACC Accumulator [15:8]
DATA_OUT[7:0] = MACC_AC2[7:0] = MACC Accumulator [23:16]
DATA_OUT[7:0] = MACC_AC2[7:0] = MACC Accumulator [31:24]
DATA_OUT[7:0] = MACC_AC2[7:0] = MACC Accumulator [39:32]
PRELIMINARY
000b
011b
, READs from the MACC Accumulator reg-
, reads from the MACC Accumulator regis-
eZ80190 Product Specification
Multiply-Accumulator
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