EM6517 ETC, EM6517 Datasheet - Page 18

• Manufacturer Part Number: EM6517
• Description: 4 BIT MICROCONTROLLER
• Manufacturer: ETC

For Metal mask selection and available resistor values refer to 19.1.2. ( mask selections are valid for ROM
versions only )
Pull-down ON : MPBPD[n] must be in place ,
Pull-down OFF: MPBPD[n] is not in place,
Pull-up ON
Pull-up OFF
Never pull-up and pull-down can be active at the same time.
For POWER SAVING one can switch off the port B pull resistors between two read phases. No cross current
flows in the input amplifier while the port B is not read. The recommended order is :
Minimum time with current on the pull resistor is 4 system clock periods, if the RC time constant is lower than 1
system clock period. Adding a NOP instruction before reading moves the number of periods with current in the
pull resistor to 6 and the maximum RC delay to 3 clock periods.
7.4.3 CMOS or Nch. Output
The port B outputs can be configured as either CMOS or Nch. open drain outputs. In CMOS both logic ‘1’ and
‘0’ are driven out on the terminal. In Nch. Open Drain only the logic ‘0’ is driven on the terminal, the logic ‘1’
value is defined by the internal pull-up resistor (if implemented), or high impedance.
© EM Microelectronic-Marin SA, 09/99, Rev. A/277
18
Figure 14. CMOS or Nch. Open Drain Outputs
P B D a ta [n ]
F re q u e n c y
O u tp u ts
Switch on the pull resistor.
Allow sufficient time - RC constant - for the pull resistor to drive the line to either V
Read the port B
Switch off the pull resistor
: MPBPU[n] must be in place,
: MPBPU[n] is not in place,
AND bit NoPdPB[n] must be ‘0’ .
OR if MPBPD[n] is in place NoPdPB[n] = ‘1’ cuts off the pull-down.
OR selecting NchOpDPB[n] = ‘1’ cuts off the pull-down.
AND bit NchOpDPB[n] must be ‘1’ ,
AND (bit PBIOCntl[n] = ‘0’ (input mode) OR if PBIOCntl[n] = ‘1’ while PBData[n] = 1. )
OR if MPBPU[n] is in place NchOpDPB[n] = ‘0’ cuts off the pull-up,
OR if MPBPU[n] is in place and if NchOpDPB[n] = ‘1’ then PBData[n] = 0 cuts the pull-up.
M U X
C M O S O u tp u t
D a ta
T ri-S ta te O u tp u t
B u ffe r : c lo s e d
FOR ENGINEERING ONLY
1
T e rm in a l
P B [n ]
I / O
P B D a ta [n ]
F r e q u e n c y
O u tp u ts
N c h . O p e n D ra in O u tp u t
M U X
T ri-S ta te O u tp u t
B u ffe r : H ig h
Im p e d a n c e fo r
D a ta = 1
EM6517
SS
A c tiv e P u ll-u p
fo r H ig h S ta te
or V
T e rm in a l
P B [n ]
DD
I / O
.