SAB80C166-M-T3 SIEMENS [Siemens Semiconductor Group], SAB80C166-M-T3 Datasheet - Page 10

• Manufacturer Part Number: SAB80C166-M-T3
• Description: 16-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

SAB 80C166/83C166
Memory Organization
The memory space of the SAB 80C166 is configured in a Von Neumann architecture which means
that code memory, data memory, registers and I/O ports are organized within the same linear
address space which includes 256 KBytes. Address space expansion to 16 MBytes is provided for
future versions. The entire memory space can be accessed bytewise or wordwise. Particular
portions of the on-chip memory have additionally been made directly bit addressable.
The SAB 83C166 contains 32 KBytes of on-chip mask-programmable ROM for code or constant
data. The ROM can be mapped to either segment 0 or segment 1.
1 KByte of on-chip RAM is provided as a storage for user defined variables, for the system stack,
general purpose register banks and even for code. A register bank can consist of up to 16 wordwide
(R0 to R15) and/or bytewide (RL0, RH0, …, RL7, RH7) so-called General Purpose Registers
(GPRs).
512 bytes of the address space are reserved for the Special Function Register area. SFRs are
wordwide registers which are used for controlling and monitoring functions of the different on-chip
units. 98 SFRs are currently implemented. Unused SFR addresses are reserved for future
members of the SAB 80C166 family.
In order to meet the needs of designs where more memory is required than is provided on chip, up
to 256 KBytes of external RAM and/or ROM can be connected to the microcontroller.
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 modes, which are as follows:
– 16-/18-bit Addresses, 16-bit Data, Demultiplexed
– 16-/18-bit Addresses, 16-bit Data, Multiplexed
– 16-/18-bit Addresses, 8-bit Data, Multiplexed
– 16-/18-bit Addresses, 8-bit Data, Demultiplexed
In the demultiplexed bus modes, addresses are output on Port 1 and data is input/output on Port 0.
In the multiplexed bus modes both addresses and data use Port 0 for input/output.
Important timing characteristics of the external bus interface (Memory Cycle Time, Memory Tri-
State Time, Read/Write Delay and Length of ALE, i.e. address setup/hold time with respect to ALE)
have been made programmable to allow the user the adaption of a wide range of different types of
memories. In addition, different address ranges may be accessed with different bus characteristics.
Access to very slow memories is supported via a particular ‘Ready’ function. A HOLD/HLDA
protocol is available for bus arbitration.
For applications which require less than 64 KBytes of external memory space, a non-segmented
memory model can be selected. In this case all memory locations can be addressed by 16 bits and
Port 4 is not required to output the additional segment address lines.
Semiconductor Group
9