Series EJ, ET, EY, FJ & FR
102002-177 Rev M2
48
\1020\02177M2.doc 17 Jun 2019
Byte 15 represents the digital control data. The digital control byte is assigned as
follows (only the least significant four bits are encoded into the ASCII byte):
Bit 0 HV Off (Off = 1)
Bit 1 HV On (On = 1)
Bit 2 Perform Reset (reset = 1). Sets V = 0, I = 0 &
HV Enable = off,
Bit 3 Unused
The digital control nibble will therefore contain 0001 binary = 01 hex. The ASCII
representation is (enter the number 1 at the computer keyboard):
Byte 15: 31 hex = 0011 0001 binary
The checksum is calculated on all bytes before it except the SOH character. Bytes
16 and 17 will therefore contain the remainder of a modulo 256 addition of bytes 2
through 15. In hex, these bytes are:
53 + 38 + 43 + 43 + 33 + 46 + 46 + 30 + 30 + 30 + 30 + 30 + 30 +
31 hex = 321 hex
Since modulo 256 decimal is modulo 100 hex, we can divide 321 hex by 100 hex.
The remainder is 21 hex. Therefore 21 hex will be sent in bytes 16 and 17 in ASCII
representation as 32 hex and 31 hex. Note that the actual implementation of the
checksum by the data interface is very simple and requires no actual division. The
data bytes are simply added up on an eight bit counter whose carry overflow is
ignored. The result stored in the counter will be the checksum remainder (If entering
the checksum directly from the computer keyboard, enter the numbers 2 and 1):
Byte 16: 32 hex = 0011 0010 binary
Byte 17: 31 hex = 0011 0001 binary
The last byte is the carriage return (press the “Enter” key on the computer keyboard),
represented in ASCII as:
Byte 18: 0D hex = 0000 1101 binary
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