Selecting A Window - Intel 8XC196NT User Manual

8XC196NT USER'S MANUAL
4.3.1

Selecting a Window

The window selection register (Figure 4-6) has two functions. The HLDEN bit (WSR.7) enables
and disables the bus-hold protocol (see Chapter 14, "Interfacing with External Memory"); it is
unrelated to windowing. The remaining bits select a window to be mapped into the top of the low-
er register file. Table 4-9 provides a quick reference of WSR values for windowing the peripheral
SFRs. Table 4-10 on page 4-17 lists the WSR values for windowing the upper register file.
WSR
The window selection register (WSR) has two functions. One bit enables and disables the bus-hold
protocol. The remaining bits select windows. Windows map sections of RAM into the upper section of
the lower register file, in 32-, 64-, or 128-byte increments. PUSHA saves this register on the stack and
POPA restores it.
7
HLDEN W6
Bit Bit
Number Mnemonic
7 HLDEN
6:0 W6:0
Table 4-9. Selecting a Window of 8XC196NT Peripheral SFRs
Peripheral
Ports 0, 1, 2, 6
A/D converter
EPA interrupts
EPA compare 0–1
EPA capture/compare 8–9
Timer 0–1
EPA capture/compare 0–7
4-16
W5 W4
HOLD#/HLDA# Protocol Enable
This bit enables and disables the bus-hold protocol (see Chapter 14,
"Interfacing with External Memory"). It has no effect on windowing.
1 = enable
0 = disable
Window Selection
These bits specify the window size and window number:
6 5 4 3 2 1 0
1 x x x x x x 32-byte window; W5:0 = window number
0 1 x x x x x 64-byte window; W4:0 = window number
0 0 1 x x x x 128-byte window; W3:0 = window number
Figure 4-6. Window Selection Register (WSR)
WSR Value
for 32-byte Window
(00E0–00FFH)
7EH
7DH
7CH
7BH
Address:
Reset State:
W3 W2
Function
WSR Value
for 64-byte Window
(00C0–00FFH)
3FH
3EH
3DH
14H
00H
0
W1 W0
WSR Value
for 128-byte Window
(0080–00FFH)
1FH
1EH