Echelon Series 6000 Chip databook User Manual

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symbol NEXT refers to the next element in the data stack, which is determined by contents

of the location (BP+DSP) in memory, and is thus not an actual processor register.

Figure 4. Base-Page Memory Layout

The data stack grows from low memory towards high memory, and is managed through the

DSP (Data Stack Pointer) register. Pushing a byte of data onto the data stack involves the

following steps:

1. Incrementing the DSP register
2. Storing the current contents of TOS at the address (BP+DSP) in memory
3. Moving the byte of data to TOS

Popping a byte of data from the data stack involves the following steps:

1. Moving TOS to the destination
2. Moving the contents of the address (BP+DSP) in memory to TOS
3. Decrementing the DSP register

The return stack grows from high memory towards low memory, and is managed through the

RSP (Return Stack Pointer) register. Calling a subroutine involves the following steps:

1. Storing the high byte of the instruction pointer (IP) register at the address (BP+RSP)

in memory

2. Decrementing RSP
3. Storing the low byte of IP at the address (BP+RSP) in memory
4. Decrementing RSP
5. Moving the destination address to the IP register

Similarly, returning from a subroutine involves the following steps:

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