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4152B–ASSP–09/05
A/T90FJR
5.3
External Peripheral Control Signals
CIMaX outputs a chip select EXTCS. This output is fully configurable through the Destination
Select register to be open-drain or push-pull output driver and active high or low.
The activation of this output can be programmed to be automatically the default selection when
none of the modules is selected (bit DEF = 1 in the external access auto select mask low regis-
ter) and CS input is asserted or when address match the external access auto select mask and
pattern registers on the same basis as for the modules auto selection when DEF = 0.
The EXTCS output can also be manually chosen to be the destination when AUTOSEL bit is 0 in
the Destination Select Register and when SEL = 11.
In addition, the EXTCS output can work in two ways :transmit mode or regenerate mode
selected by the XCSMOD in the Destination Select Register.
The EXTCS output reproduces the CS input whenever the external device selection conditions
are met in the CIMaX, regardless of the selection mode (automatic / manual, default / pattern
match). This mode permits to insert the CIMaX in an existing hardware architecture by replac-
ing an existing peripheral by the CIMaX on the address decoder and connecting this
peripheral to the CIMaX. The address decoding must then be set up properly on the address
decoder and in the CIMaX to match the new hardware architecture but no extra CS is needed
on the address decoder ; the CIMaX provides a new one in replacement of the one it needs.
The following table gives the maximum propagation delay according to different conditions (70
°C):
In regenerate mode, the EXTCS output acts as CEx# outputs to the modules as it is generated
by the internal CIMaX state machine in conjunction with assertion of IORD# or IOWR#. This
mode permits to access to any 8-bit peripheral accessed with a RD, a WR and a CS input such
t2 min
75 ns
37 ns
75 ns
t3
75 ns
37 ns
75 ns
t4
334 ns
185 ns
150 ns
111 ns
75 ns
185
ns
t5
75 ns
37 ns
t6 max
26 ns
t7 min
37 ns
75 ns
Memory write
IO,
EC,
Ext
600ns
250ns
200ns
150ns
100ns
Conditions
CS to EXTCS maximum time
Vcc
EXTCS Load
4.5 V
10 pF
9 ns
4.5 V
50 pF
13 ns
3.0 V
10 pF
13 ns
3.0 V
50 pF
16 ns