90E21 Datasheet, PDF (36/57 Pages) Integrated Device Technology – Single-Phase High-Performance Wide-Span Energy Metering IC

90E21/22/23/24
SINGLE-PHASE HIGH-PERFORMANCE WIDE-SPAN ENERGY METERING IC
CS2
Checksum 2
Address: 3BH
Type: Read/Write
Default Value: 0000H
15
CS2_15
7
CS2_7
14
CS2_14
6
CS2_6
13
CS2_13
5
CS2_5
12
CS2_12
4
CS2_4
11
CS2_11
3
CS2_3
10
CS2_10
2
CS2_2
9
CS2_9
1
CS2_1
8
CS2_8
0
CS2_0
Bit
Name
Description
The CS2 register should be written after the 31H-3AH registers are written. Suppose the high byte and the low byte of the 31H-
3AH registers are shown in below table.
15 - 0
CS2[15:0]
Register Address
31H
32H
33H
34H
35H
36H
37H
38H
39H
3AH
The calculatiion of the CS2 register is as follows:
High Byte
H₃₁
H₃₂
H₃₃
H₃₄
H₃₅
H₃₆
H₃₇
H₃₈
H₃₉
H_3A
Low Byte
L₃₁
L₃₂
L₃₃
L₃₄
L₃₅
L₃₆
L₃₇
L₃₈
L₃₉
L_3A
The low byte of 3BH register is: L_3B=MOD(H₃₁+H₃₂+...+H_3A+L₃₁+L₃₂+...+L_3A, 2^8)
The high byte of 3BH register is: H_3B=H₃₁ XOR H₃₂ XOR ... XOR H_3A XOR L₃₁ XOR L₃₂ XOR ... XOR L_3A
For 90E21/22/23, a part of registers are not used. These registers can be dealed as 0000H in CS calculation.
The 90E21/22/23/24 calculates CS2 regularly. If the value of the CS2 register and the calculation by the 90E21/22/23/24 is differ-
ent when AdjStart=8765H, the AdjErr[1:0] bits (SysStatus, 01H) are set.
Note: The readout value of the CS2 register is the calculation by the 90E21/22/23/24, which is different from what is written.
Register
36
January 10, 2012