XC161CJ_02 Datasheet, PDF (24/78 Pages) Infineon Technologies AG – 16-Bi t Single-Chip Microcontroller Preliminary

XC161
Derivatives
Preliminary
Functional Description
3.2
External Bus Controller
All of the external memory accesses are performed by a particular on-chip External Bus
Controller (EBC). It can be programmed either to Single Chip Mode when no external
memory is required, or to one of four different external memory access modes¹⁾, which
are as follows:
– 16 … 24-bit Addresses, 16-bit Data, Demultiplexed
– 16 … 24-bit Addresses, 16-bit Data, Multiplexed
– 16 … 24-bit Addresses, 8-bit Data, Multiplexed
– 16 … 24-bit Addresses, 8-bit Data, Demultiplexed
In the demultiplexed bus modes, addresses are output on PORT1 and data is input/
output on PORT0 or P0L, respectively. In the multiplexed bus modes both addresses
and data use PORT0 for input/output. The high order address (segment) lines use
Port 4. The number of active segment address lines is selectable, restricting the external
address space to 8 MBytes … 64 KBytes. This is required when interface lines are
assigned to Port 4.
Up to 5 external CS signals (4 windows plus default) can be generated in order to save
external glue logic. External modules can directly be connected to the common address/
data bus and their individual select lines.
Access to very slow memories or modules with varying access times is supported via a
particular ‘Ready’ function. The active level of the control input signal is selectable.
A HOLD/HLDA protocol is available for bus arbitration and allows the sharing of external
resources with other bus masters. The bus arbitration is enabled by software. After
enabling, pins P6.7 … P6.5 (BREQ, HLDA, HOLD) are automatically controlled by the
EBC. In Master Mode (default after reset) the HLDA pin is an output. In Slave Mode pin
HLDA is switched to input. This allows the direct connection of the slave controller to
another master controller without glue logic.
Important timing characteristics of the external bus interface have been made
programmable (via registers TCONCSx/FCONCSx) to allow the user the adaption of a
wide range of different types of memories and external peripherals.
In addition, up to 4 independent address windows may be defined (via registers
ADDRSELx) which control the access to different resources with different bus
characteristics. These address windows are arranged hierarchically where window 4
overrides window 3, and window 2 overrides window 1. All accesses to locations not
covered by these 4 address windows are controlled by TCONCS0/FCONCS0. The
currently active window can generate a chip select signal.
The external bus timing is related to the rising edge of the reference clock output
CLKOUT. The external bus protocol is compatible with that of the standard C166 Family.
1) _{Bus modes are switched dynamically if several address windows with different mode settings are used.}
Data Sheet
20
V1.0, 2002-03