Intel 80C196NU, 8XC196NP, Microcontroller manual Selecting a Window, Wsr, Hlden, Bit Function

8XC196NP, 80C196NU USER’S MANUAL

5.3.1Selecting a Window

The window selection register (Figure 5-5) has two functions. The HLDEN bit (WSR.7) enables and disables the bus-hold protocol (see Chapter 13, “Interfacing with External Me mory”); it is unrelated to windowing. The remaining bits select a window to be mapped into the top of the low- er register file. Window selection register 1 (Figure 5-6) selects a second window to be mapped into the middle of the 80C196NU’s lower register file.

Table 5-8 provides a quick reference of WSR values for windowing the peripheral SFRs. Table 5-9 on page 5-15 lists the WSR values for windowing the upper register file.

WSR	Address:	0014H
	Reset State:	00H

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 top 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 W5 W4

0

W3 W2 W1 W0

Bit	Bit	Function
Number	Mnemonic
7	HLDEN	HOLD#, HLDA# Protocol Enable
		This bit enables and disables the bus-hold protocol (see Chapter 13,
		“Interfacing with External Memory”). It has no effect on windowing.
		1 = enable
		0 = disable
6:0	W6:0	Window Selection
		These bits specify the window size and window number. See Table 5-8
		on page 5-15 or Table 5-9 on page 5-15.

Figure 5-5. Window Selection (WSR) Register

5-14