Jan Yin Chan Electronics Co.,LTD. 386SX Single Chip PC
M6117D : System on a chip
DM&P
Jan Yin Chan Electronics Co,. LTD. M6117D 386SX Single Chip PC Page 35
8F-1,No.22,Wuchyuan 2RD.,Hsin Chuang city Taipei Hsien, Taiwan, R.O.C. Tel: 886-(02) 2298-0770 Fax: (02) 2299-1883
4.8 Speed LED flash control
System Designer can connect an LED to M6117D CPUSPD pin to show LED flashing as a phenomenon in green mode.
There are many varieties of LED flash combination including duty cycle, just program a value to index 71h. Then LED will
start flashing.
Index 71h
Index 71h
D[4-2] LED flash period D[1-0] LED duty cycle
000 0.1 sec 00 disable
001 0.2 sec 01 25%
010 0.4 sec 10 50%
011 0.8 sec 11 75%
100 1.0 sec
101 2.0 sec
110 4.0 sec
111 8.0 sec
4.9 General Purpose Output (GPO) and General Purpose Input (GPI)
M6117D support 16 independent GPOs and GPIs. This group of GPOs does not need external 74LS373 to latch as
generate purpose output. Also this group of GPIs does not share with ISA data bus, so no external 74LS245 required.
Index 46h: Independent GPI[7-0] value. Default 00h Read only.
Index 47h: Independent GPO[7-0] value. Default 00h Read/Write.
Index 4Ch: Independent GPI[15-8]value. Default 00h Read only.
Index 4Dh: Independent GPO[15-8] value. Default 00h Read/Write.
M6117D supports another 16 expandable GPOs and 16 expandable GPIs. During normal condition, pins XD[7:0] are data
bus to peripheral devices. But during cold reset, XD[7:0] is an input pin and latched by internal register - index 68h; the pin
ENPOWER is also active at this time to latch XD[7:0] at external 74LS373. Because there is no default value in index 68h
and as to XD[7:0] without any pulling resistor. Designer has to connect externally pull-up or pull down resistors to XD[7-0] to
initialize index 68h. The index 68h : D[7-0] are both readable and writable. If BIOS wants to change the external 74LS373
latch value. It should first set index 68h :D[7:0] a new value, then write any value to index 73h, that will generate an
ENPOWER signal to update 74LS373 latch value. The index value in 68h will appear at XD[7:0] bus and ENPOWER will
update the XD value to 74LS373.
Index 3Dh: The high byte GPO value . Default 00h R/W
Index 3Eh: The low byte GPI value. Default 00h Read only.
Index 3Fh: The high byte GPI value. Default 00h Read only.
4.9.1 Generate GPOs method
(1) Use external 2 X 74373 input connect to SD bus. The latch enable pin connects to ENPOWER.
(2) Set index 68h and 3Dh to desired GPO value.
(3) Write index 73h.
(4) Then data stored in index 68h will be sent to SD[7:0] and XD[7:0]. Data stored in Index 3Dh will be sent to SD[15:8] and
ENPOWER will be active.
(5) The value will be latched by 74373.
4.9.2 Generate GPIs method
(1) Add external 2 X 74245, the input connects to GPIs, the output connects to ISA SD bus. The OE control connects to
ISA REFRESHJ.
(2) When REFRESHJ is active, the SD will become input and M6117D will use MEMRJ rising edge to latch the SD value.
(3) Every 15us, the GPIs value will be updated.
(4) BIOS can read the GPI
value through index 3Fh which store SD[15:0] value.
4.9.3 Generate Independent GPIOs as GPO method
(1) Write the desired value to index 47H , 4DH.
(2) Choose any GPIO as GPO by program GPIOE index 4EH , 4FH , and desired value will appear on independent GPO
pins right away.
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