Elan Digital Systems Ltd.
37
HD717 USER’S
GUIDE
The following table shows the indexes of the various sub-registers in
the HD717 (all are 8-bits unless stated):
SUB REG
IDX[3:0]
SUB REG read
SUB REG write
0
PCR[7:0]
PRIMARY CONTROL
REGISTER
PCR[7:0]
PRIMARY CONTROL
REGISTER
1
LBG[7:0]
LOW RATE DATA BAUD
GENERATOR REGISTER
LBG[7:0]
LOW RATE DATA BAUD
GENERATOR REGISTER
2
SCS[7:0]
SCC CLOCK SELECT
REGISTER
SCS[7:0]
SCC CLOCK SELECT
REGISTER
3
DIDI[7:0]
DIGITAL I/O PIN
INPUT DATA REGISTER
DIDO[7:0]
DIGITAL I/O PIN
OUTPUT DATA REGISTER
4
DIR[4:0]
DIGITAL I/O PIN
DIRECTION REGISTER
DIR[4:0]
DIGITAL I/O PIN
DIRECTION REGISTER
5
SCR[7:0]
SECONDARY CONTROL
REGISTER
SCR[7:0]
SECONDARY CONTROL
REGISTER
6
MSR[7:0]
MISCELLANEOUS STATUS
REGISTER
NOT USED
7
IMR[7:0]
INTERRUPT MASK
REGISTER
NOT USED
NOTE
1. All signals with an ‘n’ prefix are active low in this document.
2. All BINARY values are shown with MSBit LEFTMOST.
3. “RESERVED” means that a register bit is physically implemented
but its use is not yet defined. Observe the instruction to write the
bit to a particular state for future compatibility.
4. “NOT USED” means that a bit is physically not implemented. The
state written should be ‘0’ for future compatibility. The state read
will be ‘0’.