Mitsubishi DS907x SIP, DS5000TK DS5000 Series Memory Organization, Important Application Note

USER'S GUIDE

DS5000 Series Memory Organization

As mentioned above, the DS5000 series consists of the DS5000FP chip and the DS5000(T) and DS2250T mod- ules. The programming model discussed in this section applies to all of these parts. The DS5000 series Byte± wide bus has 15 address lines, eight data lines, a R/W strobe, and two chip enables to access nonvolatile RAM. In the case of a module, these are already con- nected and may be thought of as internal or embedded memory. The DS5000 series can use either 8K x 8 or 32K x 8 SRAMs. The user must inform the microcontrol- ler of the selected RAM size using the Range function. The Range bit resides in the MCON SFR at MCON.3 and has a value of 0 when 8K SRAM is used and 1 when a 32K byte SRAM is used. Range is selected during Bootstrap Loading and can not be varied by the applica- tion software. The DS5000 device accesses memory on its Byte±wide bus using two chip enables. The first, CE1, is Partitionable. That is, the RAM connected to CE1, whether 8K or 32K, can be divided between pro- gram and data segments. The Partition is user±se- lected and can be set during Bootstrap Loading and by software. Partitions are generally available on 2K byte boundaries in the DS5000 except for the last which is 4K. The Partition is selected using the MCON SFR de- scribed below. CE2 is restricted to data memory only. The RAM on CE2 should be of the same size as CE1. Access to CE2 is manual, and functions like a bank switch. Bit 2 (ECE2) of the MCON SFR controls access to CE2 and is described below.

Figure 4±3 illustrates the functional memory map of a DS5000 series device. The Partition, Range, ECE2, and the logical address combine to determine whether the DS5000 uses its Byte±wide bus or the Expanded

Bus. Nonvolatile RAM access will occur when the log- ical address lies in one of the shaded regions. These are program addresses below the Partition address, data addresses above the Partition and below the Range ad- dress, or data addresses between 0 and the Range when ECE2 is set to a logic 1. Note that when using ECE2 to force data access, the CE2 RAM will be se- lected instead of the CE1 RAM. This means that on a DS5000 module or a DS2250 with less than 64K RAM, no data memory exists under CE2. The ECE2 has no affect on program memory, which continues from the CE1 RAM or the Expanded bus normally.

Note that the Partition and Range settings are not auto- matically linked. This means a user should take care not to select a Partition that is larger than the Range. Natu- rally when the Range is 32K, the Partition address can be as high as 32K. When a Range of 8K is used, Parti- tion addresses below 8K should be used. Any address that does not map onto the Byte±wide bus will be auto- matically be routed to the Expanded Bus of Ports 0 and

2.For module users. this means that any address not routed to internal memory will go to the ports. The follow- ing examples will help illustrate the decoding.

When the Partition is at 3000h, and the Range at 32K, program memory below 3000h is accessed on the Byte±wide bus. Program memory at or above 3000h is directed to the Expanded bus or Ports 0 and 2. When the Partition is at 5800h and the Range at 32K, data memory at 0000h is accessed on Ports 0 and 2. Data memory at 6000h is located in NV RAM on the Byte± wide bus. When the Partition is at 1000h and the Range at 8K, all memory access above 1FFFh is on the Ex- panded bus. Below 8K, the Partition rules apply.

IMPORTANT APPLICATION NOTE

The MCON register is a special function register unique to Dallas Semiconductor microcontrollers which contains nonvolatile memory configuration information. This register should be set to the desired value before loading the device via the bootstrap loader. Failure to correctly configure the MCON register can cause the device to operate incorrectly, including symptoms which appear similar to a defective device. Because this register is nonvolatile, incor- rect memory settings will be preserved when power is removed. The DS5001FP, DS5002FP, DS2251T, and DS2252T store additional memory configuration information in the RPCTL register, which should also be set to the desired value before loading the device via the bootstrap loader.

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